Development and Validation of a Highly Nonlinear Model for Wave Propagation Over a Variable Bathymetry

Author(s):  
Maïté Gouin ◽  
Guillaume Ducrozet ◽  
Pierre Ferrant

Liu and Yue [1] developed a numerical scheme for propagating waves over a variable bathymetry with a High-Order Spectral (HOS) Method. The development of this nonlinear model is detailed and validated on three different test cases. They intend to demonstrate that such a model may be applied to small bottom variations as considered in [1] but also on cases where the bottom variation may be important. In this concern, the very well documented test case of a 2D underwater bar is studied in details. Comparisons are provided with both experimental and numerical results.

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2896
Author(s):  
David Khani ◽  
Yeo Howe Lim ◽  
Ahmad Malekpour

On the basis of the two-component pressure approach, we developed a numerical model to capture mixed transient flows in close conduit systems. To achieve this goal, an innovative Godunov finite-volume numerical scheme is proposed to suppress the spurious numerical oscillations occurring during rapid pipe pressurization. To dissipate the spurious numerical oscillations, we admit artificial numerical viscosity to the numerical scheme through applying a proposed Harten, Lax, and van Leer (HLL) Riemann solver for calculating the numerical fluxes at the computational cell interfaces. The proposed solver controls the magnitude of the numerical viscosity through adjusting the left and right wave velocities. A wave velocity calculator is proposed to optimally distribute the numerical viscosity over several computational cells around the computational cell in which the pressurization front is located. The proposed solver admits significant artificial numerical viscosity when the pipe pressurization is imminent and automatically reduces it in other places; in this way the numerical diffusion and data smearing is minimized. The validity of the proposed model is justified by the aid of several test cases in which the numerical results are compared with both experimental data and the results obtained from analytical methods. The results reveal that the proposed model succeeds in completely removing the spurious numerical oscillations, even when the pipe acoustic speed is over 1000 m/s. The numerical results also show that the model can successfully capture occurrence of negative pressures during the course of transient flow.


2019 ◽  
Vol 24 (3) ◽  
pp. 691-708 ◽  
Author(s):  
S.K. Tomar ◽  
N. Goyal ◽  
A. Szekeres

Abstract Propagation of time harmonic plane waves in an infinite thermo-viscoelastic material with voids has been investigated within the context of different theories of thermoelasticity. The equations of motion developed by Iesan [1] have been extended to incorporate the Lord-Shulman theory (LST) and Green-Lindsay theory (GLT) of thermoelasticity. It has been shown that there exist three coupled dilatational waves and an uncoupled shear wave propagating with distinct speeds. The presence of thermal, viscosity and voids parameters is responsible for the coupling among dilatational waves. All the existing waves are found to be dispersive and attenuated in nature. The phase speeds and attenuation coefficients of propagating waves are computed numerically for a copper material and compared under different theories of thermo-elasticity. The expressions of energies carried along each wave have also been derived. All the computed numerical results have been depicted through graphs. It is found that the influence of CT and GLT is almost same on wave propagation, while LST influences the wave propagation differently.


Author(s):  
Sebastian Föllner ◽  
Volker Amedick ◽  
Bernhard Bonhoff ◽  
Dieter Brillert ◽  
Friedrich-Karl Benra

Abstract In this paper the development and validation of a new meridional throughflow solver for the analysis of multistage axial turbines is presented. The quasi-three-dimensional finite-volume solver named tFlow is based on the inviscid Euler equations. To treat transonic flows with shocks the approximate Riemann solver of Roe for the computation of the inviscid fluxes in combination with the MUSCL approach are used. In the meridional plane turbine blades are numerically modeled by introducing two volume source terms for blade blockage and blade deviation effects. In this contribution four different validation test-cases are discussed. The general fluid solver is validated by analytical solutions of the established Ringleb flow and the simulation of a two-dimensional transonic nozzle flow. In contrast to prior publications [1–3] tFlow uses a different formulation of the blockage effect which is tested using the blockage data of a general convergent-divergent nozzle. Blade deviation effects are validated by comparison with three-dimensional results obtained from the commercial flow solver CFX. The results of tFlow are consistent with the analytical solutions and in case of the blade deviation test-case in good agreement to the three-dimensional results. Compared to fully three-dimensional simulations the developed solver enables faster analyses of multistage axial turbines to evaluate the performance characteristic.


2019 ◽  
Vol 23 (Suppl. 2) ◽  
pp. 623-630 ◽  
Author(s):  
Yulia Kratova ◽  
Alexander Kashkovsky ◽  
Anton Shershnev

Modification of the serial Fortran code for solving unsteady 2-D Euler equations for the mixture of compressible gas and polydisperse particles was carried out using OpenMP technology. Modified code was verified and parallel speed-up was measured. Analysis showed that the data on parallel efficiency is in a good agreement with the Amdahls law, which gives the estimate for serial code fraction about 30%. Parallel code was used for the numerical simulation of two test-cases, namely shock wave propagation in 2-D channel with obstacles filled with reactive Al-O2 gas particle mixture and heterogeneous detonation propagation in polydisperse suspensions. For the first test-case the data on particles distribution in the flow was obtained, the existense of particle free zones inside the vortices was demonstrated and the attenuation of a shock wave was studied. In the second test, numerical simulation of detonation shock wave propagation in plain 2-D channel for the three polydisperse mixtures was carried out and data on detonation regimes was also obtained.


2008 ◽  
Author(s):  
Miguel R. Visbal ◽  
Scott E. Sherer ◽  
Michael D. White

2021 ◽  
Vol 26 (4) ◽  
Author(s):  
Man Zhang ◽  
Bogdan Marculescu ◽  
Andrea Arcuri

AbstractNowadays, RESTful web services are widely used for building enterprise applications. REST is not a protocol, but rather it defines a set of guidelines on how to design APIs to access and manipulate resources using HTTP over a network. In this paper, we propose an enhanced search-based method for automated system test generation for RESTful web services, by exploiting domain knowledge on the handling of HTTP resources. The proposed techniques use domain knowledge specific to RESTful web services and a set of effective templates to structure test actions (i.e., ordered sequences of HTTP calls) within an individual in the evolutionary search. The action templates are developed based on the semantics of HTTP methods and are used to manipulate the web services’ resources. In addition, we propose five novel sampling strategies with four sampling methods (i.e., resource-based sampling) for the test cases that can use one or more of these templates. The strategies are further supported with a set of new, specialized mutation operators (i.e., resource-based mutation) in the evolutionary search that take into account the use of these resources in the generated test cases. Moreover, we propose a novel dependency handling to detect possible dependencies among the resources in the tested applications. The resource-based sampling and mutations are then enhanced by exploiting the information of these detected dependencies. To evaluate our approach, we implemented it as an extension to the EvoMaster tool, and conducted an empirical study with two selected baselines on 7 open-source and 12 synthetic RESTful web services. Results show that our novel resource-based approach with dependency handling obtains a significant improvement in performance over the baselines, e.g., up to + 130.7% relative improvement (growing from + 27.9% to + 64.3%) on line coverage.


2021 ◽  
Vol 40 (4) ◽  
pp. 1-15
Author(s):  
Siyuan Shen ◽  
Yin Yang ◽  
Tianjia Shao ◽  
He Wang ◽  
Chenfanfu Jiang ◽  
...  

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