Propagation of shock waves in dry and wet sandstone:Experimental observations,theoretical analysis and meso-scale modeling

Methods of experimental observations, theoretical analysis and meso-scale modeling were used to study the propagation processes of shock waves in dry and wet sandstone under dynamic impact in this paper.According to the results from the dynamic impact experiments with velocity of 0.2-0.5 km/s, it was found that the velocity of shock wave increases linearly with water content. Additionally, the velocity of the shock wave in the sandstone showed a linearly increased regularity with the increasement of the impact velocity, which was proved by theory in this paper. Furthermore, meso-scale simulation models were performed and the simulation results showed that sandstone's porosity reduced the shock waves velocity compared to nonporous materials. Pore space filled with water counteracts the effects of porosity, resulted in larger shock wave velocity.

A Study of the Environmental Influence on the Amplitude of Lee Waves

A three-layer theoretical model is used to calculate the lee wave of a real example occurring over Blue Ridge in Pittsburgh, in which the maximum vertical velocity is 0.11 m s^-1. Based on this, the influence of changes in the thickness and values of the Scorer parameter in each layer are analyzed. It is shown that the influence of each layer parameters on the lee-wave amplitude is different, and the amplitude is more sensitive to the changes in the lower layer. Since the environment changes can affect the Scorer parameter profile, the influence of the environment on the amplitude is studied. The results show that the amplitude will decrease in the daytime because of solar heating, and increase at night because of radiational cooling, according to observational data. The case is also simulated by the Advanced Regional Prediction System （ARPS） model. The simulated amplitude is 0.089 m s^-1, which is close to the calculated result. Numerical sensitivity experiments are performed to test the former calculated experiments. The simulated results are consistent with the analytically calculated results.

Analysis on the Meso-scale System Activity and the Structure Characteristics of A Short-time Rainstorm

By using the rainfall data in the regional automatic station,FY-2E satellite data,NCEP reanalysis data,the evolution features and the structure characteristics of a meso-scale convective system(MCS) which happened on May 6 in 2010 in Loudi City of Hunan Province were analyzed.The results showed that MCS was the important influence system for the generation and development of strong precipitation.The equivalent blackbody brightness temperature(TBB) field of satellite inversion could directly reflect the convective activity of cumulus,the precipitation distribution and the intensity characteristics in the rainstorm process.TBB low value belt had the good corresponding relationship with the rainstorm falling zone.The disturbance flow field and the height field which passed Barnes band-pass wave filtering represented that there existed the obvious high-layer anticyclonic circulation and the low-layer cyclonic circulation near the rainstorm zone.The divergence in the high layer and the convergence in the low layer enhanced the occurrence and development of MCS.In addition,the disturbance temperature field revealed the main source of energy which the occurrence and development of strong convective weather needed.

The energy conversion rates from eddies and mean fl ow into internal lee waves in the global ocean

Internal lee waves play an important role in transferring energy from eddies to small scale mixing.However,the energy conversion from eddies into lee waves in the global ocean remains poorly understood.Conversion rates from eddies and from mean fl ow in the global ocean were diff erentiated using single beam sounding data,stratifi cation from climatology,eddy velocity,and mean fl ow from a global ocean model.The global integral energy conversion from eddies is estimated to be 0.083 TW and is almost twice as that from the mean fl ow.A new method was developed to study the uncertainties of energy conversion caused by dealing with the topographic data.Results show that diff erent data processing procedures,and the resolution and accuracy of topographic data have a signifi cant impact on the estimated global energy conversion.

Analysis of a simplification strategy in a nonhydrostatic model for surface and internal wave problems

This paper examines the simplification strategy of retaining only the nonhydrostatic effect of local acceleration in a three-dimensional fully nonhydrostatic model regarding the submesoscale wave phenomenon in the ocean.Elaborate scale analysis of the vertical component of the Reynold-averaged Navier-Stokes(RANS)equation was performed,confirming the rationalization of this simplification.Then,the simplification was implemented in a RANS equation-based nonhydrostatic model NHWAVE(nonhydrostatic WAVE)to make a simplified nonhydrostatic model.Numerical examples were taken to test its performance,including surface sinusoidal waves propagating on an idealized East China Sea topography,tidally induced internal lee waves and small-scale solitary waves.The results show that in a considerably wide range of nonlinear strengths,the simplified nonhydrostatic model can obtain similar results as those in the fully nonhydrostatic model,even for smaller-scale solitary waves.Nonlinearity influences the applicability of the simplification.The stronger the nonlinearity is,the worse the simplified model describes the nonhydrostatic phenomenon.In general,the simplified nonhydrostatic model can simulate surface waves better than internal waves.Improvement of computational efficiency in the simplified nonhydrostatic model is reasonable,reducing the central processing unit time duration in the fully nonhydrostatic model by 16.4%–20.6%.The specially designed algorithm based on the simplified nonhydrostatic equation can remarkably reduce the computational time.

Chen-Lee-Liu方程的精确解

研究在非线性光学等领域出现的Chen-Lee-Liu(CLL)方程的精确解.通过对CLL方程的行波约化导出一个具有高次非线性项的非线性常微分方程.为了解该非线性常微分方程,给出一个新的辅助微分方程及其精确解.借助该辅助微分方程及其精确解,并根据齐次平衡原则,得到CLL方程的包络孤立波解和包络正弦波解.所用方法可应用到其它类似方程的求解.

Chen-Lee-Liu方程的精确解

研究在非线性光学等领域出现的Chen-Lee-Liu方程的精确解,通过对其行波约化,导出一个具有高次非线性项的非线性常微分方程,并运用已知常微分方程的解直接得到Chen-Lee-Liu方程的多组精确解。

The Cyclic Behavior of Mountain Gravity Waves Generated by Flow over Topography

The cyclic behavior of lee wave systems, generated by stratified flow over mountains is investigated by the Advanced Regional Prediction System (ARPS) model. The results show that, surface friction has a direct impact upon the number and timing of mountain gravity waves cycle generation. Cyclic generation of mountain lee waves and down-slope winds was found to be extremely sensitive to the magnitude of the surface drag coefficient, where mountain waves amplitude and intensity varies with the magnitude of the drag coefficient, and the interaction of mountain waves and boundary layer process determinates the wave characteristics. For the typical drag Cd = 10–3, surface friction promotes the formation of the stationary mountain lee waves and hydraulic jump, especially, promotes boundary layer separation, the generation of low-level turbulent zones and rotor circulation or reversal flow within boundary layer. When drag coefficient becomes Cd = 10–4, lee waves remain steady states and the first evolution cycle maintains much longer than that of Cd = 10–3. In the case of the highest drag coefficient Cd = 10–2, surface friction suppresses wave breaking and the onset of hydraulic jump, and reduces greatly the amplitude and intensity of lee waves and down slope wind.

NUMERICAL SIMULATION OF TYPHOON WAVE UNDER THE INFLUENCE OF WINNIE (NO. 9711)

In this paper, the wind field provided by a meso-scale atmospheric model is employed. When main physical processes, including wave-current interactions, are considered, the latest version of the third generation wave model SWAN is applied to simulate the typhoon wave generated by Typhoon Winnie. The model results are compared with the TOPEX/POSEIDON and ERS-2 satellite altimeter data and analyzed in details. Then the distribution of wave fields are analyzed, with the results showing that applying SWAN to simulate large-scale domain can also fairly reproduce the observed features of waves and realistically reflect the distribution of typhoon waves.

遗传算法对Lee模型的本地化修正

Lee模型在不同区域不同环境中具有较大误差,针对这个问题,提出了一种基于遗传算法对Lee模型的修正。将Lee模型的参数作为变量,用实测值与预测值的最小均方误差作为适应度函数应用在遗传算法中,实现了Lee模型本土优化。根据大量实测数据显示,修正后的Lee模型实测值与预测值的均方误差为5.7dB,具有可行性。

Numerical Consideration of Chen-Lee-Liu Equation through Modification Method for Various Types of Solitons

The purpose of the current study is to assess the effectiveness and exactness of the new Modification of the Adomian Decomposition (MAD) method in providing fast converging numerical solutions for the Chen-Lee-Liu (CLL) equation. In addition, we are able to simulate the scheme and provide a comparative analysis with the help of some exact soliton solutions in optical fibers. Finally, the MAD method uncovered that the strategy is proven to be reliable due to the elevated level of accuracy and less computational advances, as demonstrated by a series of tables and figures.

跃变分层流体中球体内波散度场特征实验研究

本文对跃变分层流体中匀速拖曳运动球体内波诱导流场PIV试验测量得到的水平速度散度场随时间的演化过程及内波时频、波谱、传播速度等特征进行了研究。球体处于跃层中,测试水平面位于球心下方一倍直径处。分析获得了速度散度场整体特征及其随内傅氏数F_(ri)=U/N_(max)D的变化规律,比较分析了体效应内波(Lee波)和尾流效应内波(WIW波)的时频、波谱、传播速度等波动特征。研究表明:(1)在低F_(ri)时Lee波占优,水平速度散度等值线呈内凹的“>”形,在最大浮力振荡频率f_(max)附近有非常明显的频率主峰,速度散度曲线的波谱主峰也非常明显,内波传播速度与球体运动速度基本一致;(2)在高F_(ri)时WIW波占优,水平速度散度等值线呈“■”形,频谱曲线上明显存在多个峰,且主频接近球体潜深位置当地浮力振荡频率,波谱曲线上也存在多个较明显的峰,对应WIW波波长在2.4D~5.6D之间,传播速度远低于球体运动速度;(3)在高F_(ri)时WIW波分界线的斜率与参数F_(ri)呈指数分布,在低F_(ri)下Lee波包络线的斜率也符合此分布规律。

Use of Targeted Orographic Smoothing in Very High Resolution Simulations of a Downslope Windstorm and Rotor in a Sub-tropical Highland Location

Nested simulations of a downslope windstorm over Cangshan mountain,Yunnan,China,have been used to demonstrate a method of topographic smoothing that preserves a relatively large amount of terrain detail compared to typical smoothing procedures required for models with terrain-following grids to run stably.The simulations were carried out using the Met Office Unified Model(MetUM)to investigate downslope winds.The smoothing method seamlessly blends two terrain datasets to which uniform smoothing has been applied—one with a minimum of smoothing,the other smoothed more heavily to remove gradients that would cause model instabilities.The latter dataset dominates the blend where the steepest slopes exist,but this is localised and recedes outside these areas.As a result,increased detail is starkly apparent in depictions of flow simulated using the blend,compared to one using the default approach.This includes qualitative flow details that were absent in the latter,such as narrow shooting flows emerging from roughly 1-2 km wide leeside channels.Flow separation is more common due to steeper lee slopes.The use of targeted smoothing also results in increased lee side temporal variability at a given point during the windstorm,including over flat areas.Low-/high-pass filtering of the wind perturbation field reveals that relative spatial variability above 30 km in scale(reflecting the background flow)is similar whether or not targeting is used.Beneath this scale,when smoothing is targeted,relative flow variability decreases at the larger scales,and increases at lower scales.This seems linked to fast smaller scale flows disturbing more coherent flows(notably an along-valley current over Erhai Lake).Spatial variability of winds in the model is unsurprisingly weaker at key times than is observed across a local network sampling mesoscale variation,but results are compromised due to relatively few observation locations sampling the windstorm.Only when targeted smoothing is applied does the model capture the downslope windstorm's extension over the city of Dali at the mountain's foot,and the peak mean absolute wind.

基于数值模式评估细尺度参数化方案在南大洋背风波生成源地的适用性

验证基于GM(Garret-Munk)大洋内波普适谱的细尺度参数化方案在不同海域的适用性,对于湍流混合研究来说非常重要。包含背景GM内波场的高分辨率数值模式被用于评估细尺度参数化方案在背风波生成源地处的适用性。细尺度参数化方案主要包括基于剪切的G89 (Gregg 1989)方案、基于应变的W93 (Wijesekera 1993)方案、基于剪切和应变的GHP (Gregg-Henyey-Polzin)方案以及对GHP方案中的频率矫正项作出变换的IH (Ijichi-Hibiya)方案。计算结果显示,背风波的生成伴随着海底上方近惯性内波的增强,使得内波场的动能与势能的比值相较于GM内波场偏大。在这种情况下,基于剪切的G89方案会因为高估内波场的总能量而高估耗散率。反之,基于应变的W93方案会因为低估内波场的总能量而低估耗散率。计算结果还显示,已经考虑了内波谱变形的GHP方案仍然会高估耗散率,但IH方案能比较准确地估算耗散率。

Loop Quantum Gravity Harmonic Oscillator

Attempts to unify Gravity Theory and Quantum Field Theory (QFT) under Loop Quantum Gravity Theory (LQG), are diverse;a dividing line between classical and quantum is sought with Schrödinger cat-state experiments. A Primordial Field Theory-based alternative is presented, and a gravity-based harmonic oscillator developed. With quantum theory applied at micro-scales and gravity theory at meso- and macro-scales, this scale-gap contributes to the conceptual problems associated with Loop Quantum Gravity. Primordial field theory, spanning all scales, is used to conceptually stretch key ideas across this gap. An LQG interpretation of the wave function associated with the oscillator is explained.

中尺度地形背风波的作用及其应用

文中探讨了中尺度地形背风驻波及对天气系统发生发展的影响问题，通过建立一个含类似大别山地形作用的简化数学模型并进行了数值计算，结果表明，当过山气流u取１０１ｍ／ｓ量级，层结参数Ｎ取１０(－３)ｓ(－１)量级，其比值Ｕ／Ｎ约为３×１０３～４×１０３时可出现一种相当正压的地形背风波，其波长近于Ｕ／ｆ～１０２ｋｍ（ｆ为柯氏参数）。结合上述理论结果和实际暴雨个例，分析指出在江淮梅雨期间，当有移动性的暴雨区移至大别山定常背风波的适当位置时，暴雨会得到增幅。

分层流体中细长体生成内波的试验研究

在密度连续分布的3层流体中,对细长体运动生成的内波问题进行了模型试验研究.采用多通道电导率阵,测量分析了拖曳模型产生内波的相关速度、垂向位移场及其波形结构.结果表明,拖曳模型产生的内波可以分为两类:一类是由定常源激发的Lee波;另一类是由非定常源激发的尾迹波,而且Lee波转换为尾迹波的临界内Fr=4.

关中东部连续性冰雹特征分析

利用关中东部各气象站和各县防雹站(点)建站以来的连续性降雹资料,统计分析了连续性降雹的时空分布、环流形势、物理量场以及强回波移动規律,总结出影响关中东部连续性降雹的重要天气特征及渭北多雹和多连续性降雹的重要原因是特殊地形与秦岭背风波相叠加的结果。

大地形背风波的转槽实验研究

文中利用转槽在相似定律及动力无量纲数的控制下 ,对旋转层结流越过大地形产生的背风波做了一系列的实验。实验及分析结果表明 ,无量纲数中 Froude数是最重要的参数 ,发现在层结适当时背风波同旋涡结构在山的下风方同时出现。在无旋转情况下 ,在 Froude数适当时仍然存在着明显的背风波 ,但旋转的作用能增加背风波的波动幅度 ,特别是起着引发下坡流的作用。

三维三层背风波的理论和数值研究

建立了一个三维三层背风波的理论模型,求出当Scorer参数满足中间层大,上、下两层小的情况下,三维三层背风波的理论波长和扰动分布。利用该理论模型对一个实际的背风波个例进行了计算,得到的理论波长与实际波长十分接近。理论结果还表明波动的最大扰动振幅在中层附近。利用ARPS(The Advanced Regional Prediction System)模式对此个例模拟的结果表明,模拟得到的波长、锲角及波动位相的分布都与理论模型的结果较为一致。