Megaripple dynamics on a dissipative sandy beach
Megaripple dynamics on a dissipative sandy beach
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DOI：
10.2112/si70-032.1
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发表时间：
2014-02
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影响因子：
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通讯作者：
Jon Miles;A. Thorpe;P. Russell;G. Masselink
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文献类型：
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作者：
Jon Miles;A. Thorpe;P. Russell;G. Masselink
Miles， J., Thorpe， A., Russell， P., Masselink， G., 2014。耗散沙滩上的巨涟漪动力学。见：Green， A.N.和Cooper， J.A.G.（编），《第13届国际海岸研讨会论文集》（南非德班），《海岸研究杂志》，特刊第70期，第187-192页，ISSN 0749-0208。传统的床面尺寸力模型将床面波长和高度与波轨道偏移和波轨道速度联系起来。然而，自组织模型表明，波束要么增长，要么保持稳定，要么被抹平，但不能缩短长度。本文介绍了在英国Perranporth的大潮沙耗散海滩上使用沙纹剖面仪测量的巨纹演变。当潮汐在仪器上涨落时进行测量，产生了12个不同潮汐的移动冲浪区的横截面。水深1 ~ 6米，浪高可达2.2米。这些数据可以观测到高度达30厘米、波长达1.8米的超大涟漪。在长度和高度上都观察到巨果的生长和衰减。巨纹间距随波龄的增加不一致。megariple的长度变化速度可达5厘米/分钟，高度变化速度可达0.5厘米/分钟。在大轨道速度条件下变化最大。在轨道速度为0.5 m/s时，波纹试图稳定在与轨道偏移相关的波长上，这表明存在强迫模式。最稳定的波纹具有最大的高度和陡度。在轨道速度< 0.5 m/s时，轨道间距大于轨道偏移，表明自组织生长可能是更适合小轨道速度的模型。
ABSTRACT Miles, J., Thorpe, A., Russell, P., Masselink, G., 2014. Megaripple dynamics on a dissipative sandy beach. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 187–192, ISSN 0749-0208. Conventional force models of bedform dimensions link bedform wavelength and height to wave orbital excursion and wave orbital velocity. Self-organization models, however, suggest that bedform wavelengths either: grow, remain stable, or are wiped flat, but are unable to reduce in length. This paper presents measurements of megaripple evolution on a macrotidal sandy dissipative beach at Perranporth, England, using measurements from a Sand Ripple Profiler. Measurements were made as the tide flooded and ebbed over the instruments, producing a cross-section of the moving surf zone for 12 separate tides. Water depths varied from 1 to 6 m, and wave heights were up to 2.2 m. The data allowed megaripple dimensions to be observed with heights up to 30 cm and wavelengths up to 1.8 m. Megaripples were observed to grow and decay in both length and height. Megaripple spacing did not increase consistently with age of ripple. Megaripple lengths changed at rates of up to 5 cm/minute, and height changed at rates of up to 0.5 cm/minute. Maximum changes took place in large orbital velocity conditions. At orbital velocities > 0.5 m/s, ripples attempted to stabilize at a wavelength related to the orbital excursion, suggesting a forced mode. The most stable ripples had the greatest height and steepness. At orbital velocities < 0.5 m/s the spacing was greater than the orbital excursion, suggesting self-organized growth may be a more appropriate model for small orbital velocities.