2018 Vol. 40, No. 5
Display Method:
2018, 40(5): .
Abstract:
2018, 40(5): .
Abstract:
2018, 40(5): 1-14.
doi: 10.3969/j.issn.0253-4193.2018.05.001
Abstract:
The phenomena of hypoxia and acidification in river estuary and offshore areas are increasing influenced by the anthropogenic activities and global change. The problem has being a hot topic in scientific researches and aroused an extensive attention. This is a review about the marine hypoxia and acidification indicated by microscopic features in the benthic foraminiferal tests, and summarized the theoretical basis and methods of these indicators using on the test features (diameter and weight), pore features (density, size and shape), test ornamentation (teeth and/or tubercules, flaps), test dissolution and abnormal tests caused by the recalcification, and identified the interference factors in the results. We have pointed out several problems needed to pay more attention in the future researches, raised some operable advices and research orientations. The paper also aimed to more exactly use the indicators mentioned above in the future studies of our coastal hypoxia and acidification environment, and be used in the similar palaeoenvironmental evolution.
The phenomena of hypoxia and acidification in river estuary and offshore areas are increasing influenced by the anthropogenic activities and global change. The problem has being a hot topic in scientific researches and aroused an extensive attention. This is a review about the marine hypoxia and acidification indicated by microscopic features in the benthic foraminiferal tests, and summarized the theoretical basis and methods of these indicators using on the test features (diameter and weight), pore features (density, size and shape), test ornamentation (teeth and/or tubercules, flaps), test dissolution and abnormal tests caused by the recalcification, and identified the interference factors in the results. We have pointed out several problems needed to pay more attention in the future researches, raised some operable advices and research orientations. The paper also aimed to more exactly use the indicators mentioned above in the future studies of our coastal hypoxia and acidification environment, and be used in the similar palaeoenvironmental evolution.
2018, 40(5): 15-23.
doi: 10.3969/j.issn.0253-4193.2018.05.002
Abstract:
Tsunami can be guided by oceanic ridges propagation as trapped waves transferring energy to thousands of kilometers away, which threatens the safety of harbor and coastal. Based on the linear shallow water approximation, analytical solutions of trapped waves over a hyperbolic-cosine squared ocean ridge are derived, which could be described by combining the associated Legendre functions of the first and second kinds. The corresponding dispersion relation is also obtained. For various fixed frequency ω, there are infinite wavenumber ky satisfied the dispersion relation. MIKE21-BW was used to simulate tsunami generated on the top of the ridge and propagation along it. The results show that only small part of the energy transfers as free waves and most of it is rapped over the ridge. The trapped wave propagates as traveling wave along the ocean ridge. The envelope of trapped waves is prolonged while the maximum amplitude decreases and the number of the trapped waves increases. The energy of trapped wave is mainly composed of two parts:solitary wave characteristic component with different frequencies travelling with the same speed and dispersive wave characteristic component with fixed frequency range.
Tsunami can be guided by oceanic ridges propagation as trapped waves transferring energy to thousands of kilometers away, which threatens the safety of harbor and coastal. Based on the linear shallow water approximation, analytical solutions of trapped waves over a hyperbolic-cosine squared ocean ridge are derived, which could be described by combining the associated Legendre functions of the first and second kinds. The corresponding dispersion relation is also obtained. For various fixed frequency ω, there are infinite wavenumber ky satisfied the dispersion relation. MIKE21-BW was used to simulate tsunami generated on the top of the ridge and propagation along it. The results show that only small part of the energy transfers as free waves and most of it is rapped over the ridge. The trapped wave propagates as traveling wave along the ocean ridge. The envelope of trapped waves is prolonged while the maximum amplitude decreases and the number of the trapped waves increases. The energy of trapped wave is mainly composed of two parts:solitary wave characteristic component with different frequencies travelling with the same speed and dispersive wave characteristic component with fixed frequency range.
2018, 40(5): 24-36.
doi: 10.3969/j.issn.0253-4193.2018.05.003
Abstract:
The shoreline erosion could be efficiently protected by the system of wave attenuation composed of seagrass. The primary objective of the study based on the experiment of Sánchez-González was to investigate the effects of wave nonlinearity on wave dissipation by seagrass. The results showed that the effects of wave steepness and relative water depth on wave damping factor depend on the submergence ratio of seagrass. For a given relative wave height, the drag coefficient increased with an increasing relative water depth. For a given relative water depth, the drag coefficient decreased as wave steepness increased. There were some differences between regular and irregular wave conditions for the effects of wave nonlinearity on wave attenuation. Whether dimensionless parameters, such as Keulegan-Carpenter, Reynolds number, Ursell number, are a better predictor of drag coefficients or not depends on accounting for the effects of wave nonlinearity on drag coefficients.
The shoreline erosion could be efficiently protected by the system of wave attenuation composed of seagrass. The primary objective of the study based on the experiment of Sánchez-González was to investigate the effects of wave nonlinearity on wave dissipation by seagrass. The results showed that the effects of wave steepness and relative water depth on wave damping factor depend on the submergence ratio of seagrass. For a given relative wave height, the drag coefficient increased with an increasing relative water depth. For a given relative water depth, the drag coefficient decreased as wave steepness increased. There were some differences between regular and irregular wave conditions for the effects of wave nonlinearity on wave attenuation. Whether dimensionless parameters, such as Keulegan-Carpenter, Reynolds number, Ursell number, are a better predictor of drag coefficients or not depends on accounting for the effects of wave nonlinearity on drag coefficients.
2018, 40(5): 37-47.
doi: 10.3969/j.issn.0253-4193.2018.05.004
Abstract:
The probability distribution characteristics of wind speed in the northern part of the South China Sea are analyzed based on buoy and oil platform sites within 0-200 km different offshore distance. Observation results indicate that the maximum average wind speed is strongest in the winter season and weakest in the summer, and the average wind speed rise gradually with the increase of the offshore distance. A two parameters Weibull distribution structure is modeled well in the observed sea surface wind speed from stations within the offshore distance area (<100 km), but the feature of sea surface wind speed of the stations outside of 100 km can not account for the Weibull structure, and the average wind speed and wind speed standard deviation arise with the increase of distance from the shore. The skewness of the wind speed is a concave downward function of the ratio of the mean wind speed to its standard deviation, such that the skewness is positive where the ratio is relatively small. The observed skewness of offshore distance stations are obviously smaller than corresponding Weibull skewness, which indicate that non-Weibull structure behavior is evident in these stations.
The probability distribution characteristics of wind speed in the northern part of the South China Sea are analyzed based on buoy and oil platform sites within 0-200 km different offshore distance. Observation results indicate that the maximum average wind speed is strongest in the winter season and weakest in the summer, and the average wind speed rise gradually with the increase of the offshore distance. A two parameters Weibull distribution structure is modeled well in the observed sea surface wind speed from stations within the offshore distance area (<100 km), but the feature of sea surface wind speed of the stations outside of 100 km can not account for the Weibull structure, and the average wind speed and wind speed standard deviation arise with the increase of distance from the shore. The skewness of the wind speed is a concave downward function of the ratio of the mean wind speed to its standard deviation, such that the skewness is positive where the ratio is relatively small. The observed skewness of offshore distance stations are obviously smaller than corresponding Weibull skewness, which indicate that non-Weibull structure behavior is evident in these stations.
2018, 40(5): 48-61.
doi: 10.3969/j.issn.0253-4193.2018.05.005
Abstract:
The impacts of assimilation of radar radial velocity data (Vr) using ensemble-variational (En3DVAR) data assimilation system based on the Weather Research and Forecasting model (WRF) data assimilation system (WRFDA) for the application of analyses and forecasts for Typhoon Saomai (2006) are investigated. The Vr data at 30-min intervals are assimilated into the WRF model at a cloud-resolving scale using the three-dimensional variational data assimilation (3DVAR) and En3DVAR respectively, over a 3 hour before its landfall. The root-mean-square errors of the Vr data by the En3DVAR were smaller than those by the 3DVAR for Typhoon Saomai. Experiments showed that such improvements were due to the use of the flow-dependent ensemble covariance provided by En3DVAR system. Positive temperature increments are found in Hybrid-En3DVAR experiments, indicating a warming of the inner core with a more realistic thermal structure throughout the depth of the hurricane. In contrast, 3DVAR experiment produces much weaker and smoother increments with negative values at the vortex center at lower levels. In additional, it was found that the En3DVAR, using the flow-dependent covariance that gave the hurricane-specific error covariance estimates, was able to systematically adjust the position of the hurricane during the assimilation whereas the 3DVAR was not. Overall, the analysis and forecasts of the En3DVAR scheme are superior to the 3DVAR scheme assimilating the same Vr Observations.
The impacts of assimilation of radar radial velocity data (Vr) using ensemble-variational (En3DVAR) data assimilation system based on the Weather Research and Forecasting model (WRF) data assimilation system (WRFDA) for the application of analyses and forecasts for Typhoon Saomai (2006) are investigated. The Vr data at 30-min intervals are assimilated into the WRF model at a cloud-resolving scale using the three-dimensional variational data assimilation (3DVAR) and En3DVAR respectively, over a 3 hour before its landfall. The root-mean-square errors of the Vr data by the En3DVAR were smaller than those by the 3DVAR for Typhoon Saomai. Experiments showed that such improvements were due to the use of the flow-dependent ensemble covariance provided by En3DVAR system. Positive temperature increments are found in Hybrid-En3DVAR experiments, indicating a warming of the inner core with a more realistic thermal structure throughout the depth of the hurricane. In contrast, 3DVAR experiment produces much weaker and smoother increments with negative values at the vortex center at lower levels. In additional, it was found that the En3DVAR, using the flow-dependent covariance that gave the hurricane-specific error covariance estimates, was able to systematically adjust the position of the hurricane during the assimilation whereas the 3DVAR was not. Overall, the analysis and forecasts of the En3DVAR scheme are superior to the 3DVAR scheme assimilating the same Vr Observations.
2018, 40(5): 62-74.
doi: 10.3969/j.issn.0253-4193.2018.05.006
Abstract:
Based on available seismic, well and regional geology data, tectonic subsidence and extension degree of the Wan'an Basin were calculated by balanced cross-section and backstripping techniques to reconstruct tectonic evolution history of the basin and further probe into its genetic mechanism. The results indicate that tectonic subsidence curves are composed of multiple-line sections and there exists differential subsidence in the northern and southern basin, and the subsidence center of the whole gradually shifts southward. Two subsidence centers developed in Late Eocene to Oligocene (37.8-23.0 Ma BP) and tectonic subsidence mainly concentrated in the middle and northern basin, while the southern part of the basin subsided rapidly in Early Miocene (23.03-16.0 Ma BP) and there exists three subsidence centers. However, tectonic subsidence has decreased since the Middle Miocene (~16.0-11.63 Ma BP) and the whole basin has entered into post-rift thermal subsidence stage. Basin extension is closely related to the seafloor spread of South China Sea and the stretching in the middle-northern basin is earlier than the southern basin. It is inferred that alternating sinistral to dextral strike-slip motions along the Wan'an Fault Zone control on the formation and evolution of Wan'an Basin, as a result of rifting and strike-slipping. The basin tectonic evolution is divided into four stages:initial rift, syn-rift, strike-slip reformation, and post-rift accelerated thermal subsidence stages.
Based on available seismic, well and regional geology data, tectonic subsidence and extension degree of the Wan'an Basin were calculated by balanced cross-section and backstripping techniques to reconstruct tectonic evolution history of the basin and further probe into its genetic mechanism. The results indicate that tectonic subsidence curves are composed of multiple-line sections and there exists differential subsidence in the northern and southern basin, and the subsidence center of the whole gradually shifts southward. Two subsidence centers developed in Late Eocene to Oligocene (37.8-23.0 Ma BP) and tectonic subsidence mainly concentrated in the middle and northern basin, while the southern part of the basin subsided rapidly in Early Miocene (23.03-16.0 Ma BP) and there exists three subsidence centers. However, tectonic subsidence has decreased since the Middle Miocene (~16.0-11.63 Ma BP) and the whole basin has entered into post-rift thermal subsidence stage. Basin extension is closely related to the seafloor spread of South China Sea and the stretching in the middle-northern basin is earlier than the southern basin. It is inferred that alternating sinistral to dextral strike-slip motions along the Wan'an Fault Zone control on the formation and evolution of Wan'an Basin, as a result of rifting and strike-slipping. The basin tectonic evolution is divided into four stages:initial rift, syn-rift, strike-slip reformation, and post-rift accelerated thermal subsidence stages.
2018, 40(5): 75-89.
doi: 10.3969/j.issn.0253-4193.2018.05.007
Abstract:
Source, transportation and fate of marine sediment are among the crucial questions in oceanographic sedimentology. As well known, the materials of so called Zhe-Min coastal mud are mainly derived from the Changjiang River as well as the medium and small rivers throughout Zhejiang and Fujian Provinces. However, we still have little knowledge on the quantitative contribution of those medium and small rivers to that mud zone, probably due to the lack of suitable tracers. Using grain-size end member and clay minerals as tracers, this paper aims to 1) evaluate the efficiency of two tracers comprehensively, and 2) quantify the individual contribution of Jiaojiang River and Oujiang River. An end member model was used to analyze the grain size data of surficial sediment samples and 4 end members were identified. End-member 1 is attributed to the Changjiang River input. End-member 2 is caused by the input of small rivers, such as Jiaojiang River and Oujiang River. End-member 3 is associated with the input from the south part of study area and probably indicates a possible transport towards the north. End-member 4 is possibly transported from the residual sandy area. Furthermore, the graph of standard deviation values of grain-size content against grain-size classes of six cores in the mud area reveals characteristic populations of grain-size. It shows that all cores have a common characteristic population (primary peak) of grain size between 3.91 to 9.29 μm, which is associated with the fine particles suspended from the Changjiang River delta and perhaps indicates that the overall study area is affected by Changjiang River. Based on a matrix method model, data of clay minerals contents are used to evaluate the quantitative contribution of Changjiang River, Jiaojiang River and Oujiang River to the coastal muds. Due to the dependence of the clay minerals on the grain-size, the results merely reflect the contribution of fine particles less than 2 μm. In comparison, the end members of grain-size are better tracers which include the entire level of fraction to simultaneously solve both of problems about "source and quantification" in a relatively closed system. Therefore, the end-member analysis of grain size is expected to play a significant role in the future.
Source, transportation and fate of marine sediment are among the crucial questions in oceanographic sedimentology. As well known, the materials of so called Zhe-Min coastal mud are mainly derived from the Changjiang River as well as the medium and small rivers throughout Zhejiang and Fujian Provinces. However, we still have little knowledge on the quantitative contribution of those medium and small rivers to that mud zone, probably due to the lack of suitable tracers. Using grain-size end member and clay minerals as tracers, this paper aims to 1) evaluate the efficiency of two tracers comprehensively, and 2) quantify the individual contribution of Jiaojiang River and Oujiang River. An end member model was used to analyze the grain size data of surficial sediment samples and 4 end members were identified. End-member 1 is attributed to the Changjiang River input. End-member 2 is caused by the input of small rivers, such as Jiaojiang River and Oujiang River. End-member 3 is associated with the input from the south part of study area and probably indicates a possible transport towards the north. End-member 4 is possibly transported from the residual sandy area. Furthermore, the graph of standard deviation values of grain-size content against grain-size classes of six cores in the mud area reveals characteristic populations of grain-size. It shows that all cores have a common characteristic population (primary peak) of grain size between 3.91 to 9.29 μm, which is associated with the fine particles suspended from the Changjiang River delta and perhaps indicates that the overall study area is affected by Changjiang River. Based on a matrix method model, data of clay minerals contents are used to evaluate the quantitative contribution of Changjiang River, Jiaojiang River and Oujiang River to the coastal muds. Due to the dependence of the clay minerals on the grain-size, the results merely reflect the contribution of fine particles less than 2 μm. In comparison, the end members of grain-size are better tracers which include the entire level of fraction to simultaneously solve both of problems about "source and quantification" in a relatively closed system. Therefore, the end-member analysis of grain size is expected to play a significant role in the future.
2018, 40(5): 90-106.
doi: 10.3969/j.issn.0253-4193.2018.05.008
Abstract:
The gravity core ARC6-B11 recovered from the northern Bering Slope was analyzed to reconstruct the sedimentary record and paleoproductivity changes from 23 ka BP to the Middle Holocene. Based on geochemical, high-resolution core logging and AMS14C data the variation of sediment input and productivity of the study area and it's response to the sea-ice evolution were discussed. Our results demonstrate that, on account of the southern extended sea-ice, the paleoproductivity is low during the Last Glacial Maximum, while the sand and ice rafting debris (IRD) contents of the sediments are high. But the sand and IRD contents decreased sharply during Heinrich Stadial 1 (HS 1) cold period because of the perennial sea-ice cover. The total organic carbon (TOC) content peaks during HS 1 could not be used as the paleoproductivity indicator due to the influence of the terrigenous organic matter. The abnormal peak value of the TOC content may relates to the redisposition of the shelf clay matter suspended by the oxygen enriched water mass influenced by the sea level change and sea-ice formation. The paleoproductivity is high during Bølling/Allerød (B/A) and Holocene warm period, there are also Ca Peak Event and sedimentary laminae. The occurrence of Ca Peak Event in the B/A warming period is directly influenced by the deepening of carbonate compensation depth, but the alteration of ventilation and the coccolith bloom may play a certain role on it.
The gravity core ARC6-B11 recovered from the northern Bering Slope was analyzed to reconstruct the sedimentary record and paleoproductivity changes from 23 ka BP to the Middle Holocene. Based on geochemical, high-resolution core logging and AMS14C data the variation of sediment input and productivity of the study area and it's response to the sea-ice evolution were discussed. Our results demonstrate that, on account of the southern extended sea-ice, the paleoproductivity is low during the Last Glacial Maximum, while the sand and ice rafting debris (IRD) contents of the sediments are high. But the sand and IRD contents decreased sharply during Heinrich Stadial 1 (HS 1) cold period because of the perennial sea-ice cover. The total organic carbon (TOC) content peaks during HS 1 could not be used as the paleoproductivity indicator due to the influence of the terrigenous organic matter. The abnormal peak value of the TOC content may relates to the redisposition of the shelf clay matter suspended by the oxygen enriched water mass influenced by the sea level change and sea-ice formation. The paleoproductivity is high during Bølling/Allerød (B/A) and Holocene warm period, there are also Ca Peak Event and sedimentary laminae. The occurrence of Ca Peak Event in the B/A warming period is directly influenced by the deepening of carbonate compensation depth, but the alteration of ventilation and the coccolith bloom may play a certain role on it.
2018, 40(5): 107-117.
doi: 10.3969/j.issn.0253-4193.2018.05.009
Abstract:
The provenance of Core SO-50 sediments were discussed in this paper based on grain-size, Sr-Nd isotopes, major and trace elements and AMS14C dating. Results showed that Core SO-50 could be divided into two sedimentary units:(1) the upper unit(0-540 cm,0-3.0 ka BP), (2) the lower unit(540-571 cm,3.0-3.3 ka BP). Compared with the upper unit, the sand content increased and the content of major elements (excepting SiO2) and REE decreased. In addition to the abnormal value, the trends of 87Sr/86Sr and εNd were relatively stable. The results suggested that Core SO-50 sediments were mainly derived from the eastern Qiongzhou Strait, Taiwan islands and the surrounding coastal. In the lower unit were primarily a mixture of the eastern Qiongzhou Strait and Taiwan islands, and in the upper unit, in addition to the contribution of the eastern Qiongzhou Strait and Taiwan islands, the supply of the surrounding coastal was increased. Therefore, the contribution of Taiwan islands to the Beibu Gulf area should be paid more attention in the future studies.
The provenance of Core SO-50 sediments were discussed in this paper based on grain-size, Sr-Nd isotopes, major and trace elements and AMS14C dating. Results showed that Core SO-50 could be divided into two sedimentary units:(1) the upper unit(0-540 cm,0-3.0 ka BP), (2) the lower unit(540-571 cm,3.0-3.3 ka BP). Compared with the upper unit, the sand content increased and the content of major elements (excepting SiO2) and REE decreased. In addition to the abnormal value, the trends of 87Sr/86Sr and εNd were relatively stable. The results suggested that Core SO-50 sediments were mainly derived from the eastern Qiongzhou Strait, Taiwan islands and the surrounding coastal. In the lower unit were primarily a mixture of the eastern Qiongzhou Strait and Taiwan islands, and in the upper unit, in addition to the contribution of the eastern Qiongzhou Strait and Taiwan islands, the supply of the surrounding coastal was increased. Therefore, the contribution of Taiwan islands to the Beibu Gulf area should be paid more attention in the future studies.
2018, 40(5): 118-128.
doi: 10.3969/j.issn.0253-4193.2018.05.010
Abstract:
Rising sea-level has significant impact on coastal societies. Therefore, it is of great importance to monitor and understand how local sea level is changing. This paper used BeiDou three frequency signals which were received from Dayangshan, Zhejiang, China during September 5, 2014 to September 31, 2014, to successfully achieve the purpose of detection of tide change. Among the altimetry results, the STD (the standard deviation of the residual between the altimetry and tide) of B1 frequency is 33.82 cm and its correlation coefficient is 95.98%; the STD of B2 frequency is 38.48 cm and its correlation coefficient is 94.68%; the STD of B3 frequency is 34.56 cm and its correlation coefficient is 96.08%. This is the first study about altimetry of SNR observation using BeiDou three frequency signals. By analyzing the experiment data, it can verify its feasibility that BeiDou three frequency signals to detect the tide change. Meanwhile, each of the performance of BeiDou three frequency signals was analyzed in this paper.
Rising sea-level has significant impact on coastal societies. Therefore, it is of great importance to monitor and understand how local sea level is changing. This paper used BeiDou three frequency signals which were received from Dayangshan, Zhejiang, China during September 5, 2014 to September 31, 2014, to successfully achieve the purpose of detection of tide change. Among the altimetry results, the STD (the standard deviation of the residual between the altimetry and tide) of B1 frequency is 33.82 cm and its correlation coefficient is 95.98%; the STD of B2 frequency is 38.48 cm and its correlation coefficient is 94.68%; the STD of B3 frequency is 34.56 cm and its correlation coefficient is 96.08%. This is the first study about altimetry of SNR observation using BeiDou three frequency signals. By analyzing the experiment data, it can verify its feasibility that BeiDou three frequency signals to detect the tide change. Meanwhile, each of the performance of BeiDou three frequency signals was analyzed in this paper.
2018, 40(5): 129-139.
doi: 10.3969/j.issn.0253-4193.2018.05.011
Abstract:
Based on the principle of wave directional spectrum measurement of space borne spectrometer, simulations of signals received by spectrometer are carried out under different sea state conditions and wind speed in this paper. And four different modulation spectral estimation methods, such as periodogram method, Welch method, AR model method and minimum variance method, are used to retrieve the ocean wave spectrum. The inversion performances of various modulation spectral estimation methods mentioned above are compared. The simulation results show that for the one-dimensional wave spectrum inversion, there is no absolute superiority for the wave spectrum performance of the inversion by different modulation spectral estimation methods. And for the two-dimensional wave spectrum inversion, the periodogram method is the worst under the condition of developed ocean wave, and the inversion performances of the other three methods have no absolute superiority. For the mature wind-sea, the minimum variance method has the best inversion performance on the integral energy error and the significant wave height error, while the periodogram method has the worst inversion performance on the dominant wave direction error and the dominant wavelength error. In the swell condition, the AR model method has better performance than the other three methods. In the different sea state conditions, the inversion performance will decrease with the incidence angle. Based on these simulation results, the minimum variance method is proposed to retrieve ocean wave directional spectrum for the case that the sea surface is fully developed, and the AR model method is proposed to retrieve the ocean wave directional spectrum under swell condition.
Based on the principle of wave directional spectrum measurement of space borne spectrometer, simulations of signals received by spectrometer are carried out under different sea state conditions and wind speed in this paper. And four different modulation spectral estimation methods, such as periodogram method, Welch method, AR model method and minimum variance method, are used to retrieve the ocean wave spectrum. The inversion performances of various modulation spectral estimation methods mentioned above are compared. The simulation results show that for the one-dimensional wave spectrum inversion, there is no absolute superiority for the wave spectrum performance of the inversion by different modulation spectral estimation methods. And for the two-dimensional wave spectrum inversion, the periodogram method is the worst under the condition of developed ocean wave, and the inversion performances of the other three methods have no absolute superiority. For the mature wind-sea, the minimum variance method has the best inversion performance on the integral energy error and the significant wave height error, while the periodogram method has the worst inversion performance on the dominant wave direction error and the dominant wavelength error. In the swell condition, the AR model method has better performance than the other three methods. In the different sea state conditions, the inversion performance will decrease with the incidence angle. Based on these simulation results, the minimum variance method is proposed to retrieve ocean wave directional spectrum for the case that the sea surface is fully developed, and the AR model method is proposed to retrieve the ocean wave directional spectrum under swell condition.
2018, 40(5): 140-148.
doi: 10.3969/j.issn.0253-4193.2018.05.012
Abstract:
In ice ridges consolidation, the convective heat flux becomes critical due to the larger contact areas and surface temperature differences compared with those from level ice. In this paper, a submerging experiment was designed to determine the heat transfer coefficient (h) between fresh ice and fresh water in a free convection. A thermistor string was used to measure temperature changes while ice growth was recorded by photograph. To study the factors, the tests were carried out on different ice thickness (4.9 cm to 20.5 cm) and initial temperatures (-20℃ and-32℃). The result shows that the h exponential increased with temperature difference from 0.3 W/(m2·K) to 175 W/(m2·K). On the other hand, the variation of initial thickness and temperature was not a direct influence on h. For convective heat transfer, the boundary layer condition is central for understanding the convection between ice surface and water flowing past it. From the governing equation, the water flow in a free convection is caused by density difference, which is driven by the thermal expansion. A large temperature difference between surface and environmental water creates a thicker boundary layer, which leads to a higher h.
In ice ridges consolidation, the convective heat flux becomes critical due to the larger contact areas and surface temperature differences compared with those from level ice. In this paper, a submerging experiment was designed to determine the heat transfer coefficient (h) between fresh ice and fresh water in a free convection. A thermistor string was used to measure temperature changes while ice growth was recorded by photograph. To study the factors, the tests were carried out on different ice thickness (4.9 cm to 20.5 cm) and initial temperatures (-20℃ and-32℃). The result shows that the h exponential increased with temperature difference from 0.3 W/(m2·K) to 175 W/(m2·K). On the other hand, the variation of initial thickness and temperature was not a direct influence on h. For convective heat transfer, the boundary layer condition is central for understanding the convection between ice surface and water flowing past it. From the governing equation, the water flow in a free convection is caused by density difference, which is driven by the thermal expansion. A large temperature difference between surface and environmental water creates a thicker boundary layer, which leads to a higher h.
Email alert
RSS