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This study presents a numerical analysis of dam-break flow over a solid downstream structure, with a focus on the drag force exerted and the effects of porous media and bed slope. Dam-break events are high-energy phenomena capable of causing significant structural damage, primarily due to the intense forces involved. This research addresses a critical gap in understanding how porous media and bed slope can affect structural impacts in dam-break scenarios. Findings indicate that introducing porous media can reduce the drag force, though the degree of reduction varies with porosity. Similarly, increasing bed slope results in higher drag forces, though this effect is not uniform across slope increments. This study contributes practical recommendations on selecting effective porous media and bed slope configurations to enhance structural resilience in dam-break scenarios. These results, validated against experimental data, provide valuable guidance for both academic research and hydraulic engineering applications. [ABSTRACT FROM AUTHOR]

The dam is one of the most prominent hydraulic constructions on the world. Sediment flows into dam reservoirs because of human involvement in the dam catchment region, eventually affecting its functional storage. Density currents are a key feature of sedimentation. The use of bottom outflow gates to preserve the reservoir's usable volume is one approach of mitigating the effects of sedimentation. This could have an effect on the quality of the water as it exits the dam. The purpose of this research was to see how well salt current from lock exchanges was vented at different levels and outlet gate sizes. Based on the latest study's experiments, this is the highest venting efficiency when the location of outlets is in the quarter of the bottom of the dam. The output concentration will be equal to the average concentration of the concentrated input current, which is the best height for installing the outlet gates, based on the maximum venting efficiency demonstrated in the recent study's experiments, which may be described as the best height for the turbidity current outlet gate. Discharge efficiency increases when the intake concentration is lower. [ABSTRACT FROM AUTHOR]

Stability of two-way coupled particle-laden density current is studied with the aim of linear stability analysis. Interfacial instability can be found in density currents, which effects entrainment and the rate of effective mixing. In this paper, we investigate the density current interfacial instability using linear stability theory, considering the particles attendance. The ultimate goal is to extract the governing equation for current with particles and study the effect of different parameters on stability of such currents. Base flow has velocity and density profiles of tangent hyperbolic type. Main current and particles are studied in two separate phases. It is found that current will be more stable as [M.sub.0] ([M.sub.0] = [S.sup.*][N.sup.*] /[[rho].sup.*] where [[rho].sup.*] is the non-dimensional flow density, [S.sup.*] is the Stokes' drag coefficient, and [N.sup.*] is the particles' number density) grows, this is a result of number of particles and their radius, and also viscosity effects. The current is more stable as the growth rate increases. As the Richardson number in [M.sub.0] rises, the growth rate value decreases. As the slope of the river bed increases, the current is less stable. Key words: interfacial instability, linear stability analysis, [M.sub.0] coefficient, growth rate, Richardson number. Nous etudions la stabilite d'un courant de densite (aussi appele courant de turbidite) charge de particules avec couplage bidirectionnel, en vue d'une analyse de stabilite lineaire. On peut trouver de l'instabilite interfaciale dans les courants de densite, ce qui a des effets sur l'entrainement et le taux de melange effectif. Nous examinons ici l'instabilite interfaciale du courant de densite en utilisant la theorie de stabilite lineaire, tenant compte de la participation des particules. Le but ultime est l'obtention des equations directrices pour un courant portant des particules et d'etudier l'effet de differents parametres sur la stabilite de tels courants. Le debit de base a une vitesse et des profils de densite du type tangente hyperbolique. Le gros du courant et des particules est etudie dans deux phases differentes. Nous trouvons que le courant est plus stable lorsque [M.sub.0] croit, ([M.sub.0] = [S.sup.*][N.sup.*]/[[rho].sup.*], avec [[rho].sup.*] la densite du debit sans dimension, [S.sup.*] le coefficient de traines de Stokes et [N.sup.*] la densite de particules). Ceci resulte dunombre de particules et de leur rayon et aussi de laviscosite. Le courant est plus stable lorsque le tauxde croissance augmente; par contre, cette stabilite diminue lorsque le nombre de Richardson dans [M.sub.0] augmente. L'augmentation de la pente du lit de la riviere rend le courant moins stable. [Traduit par la Redaction] Mots-cles: instabilite interfaciale, analyse de stabilite lineaire, couplage bidirectionnel, le coefficient [M.sub.0], le nombre de Richardson, courant de densite., 1. Introduction Stratified flows are generated upon interaction of several currents with different densities. The difference in density can be due to a temperature gradient (in a lake or atmosphere), [...]

Hydrodynamic instabilities at the interface of stratified shear layers could occur in various modes and have an important role in the mixing process. In this work, the linear stability analysis in the temporal framework is used to study the stability characteristics of a particle-laden stratified two-layer flow for two different background density profiles: smooth (hyperbolic tangent) and piecewise linear. The effect of parameters, such as bed slope, viscosity, and particle size, on the stability is also considered. The pseudospectral collocation method employing Chebyshev polynomials is used to solve two coupled eigenvalue equations. Based on the results, there are some differences in the stability characteristics of the two density profiles. In the case of R = 1(R is the ratio of the shear layer thickness to the density layer thickness), the stability boundary in smooth profile is the transition from the unstable flow (where the dominant unstable mode is Kelvin-Helmholtz) to the stable one where in the piecewise linear profile this boundary is the transition from Kelvin-Helmholtz to the Holmboe mode. It is also shown that the unstable region increases with the bed slope and unstable modes amplify as the bed slope increases. For R = 5 the flow does not become stable by increasing the stratification in nonzero bed slope, and in some wavenumbers the Kelvin-Helmholtz and Holmboe modes coexist. In addition, by increasing the bed slope the growth rate of the Holmboe mode and the range of its existence decrease. As expected, the viscosity makes the current more stable, and for large values of the viscosity (small Reynolds number) the flow becomes stable at long waves (small wave numbers) for all bulk Richardson numbers. Existence of small particles does not change the instability characteristics so much, however, large particles make the flow more unstable. PACS No.: 47.35.-i. Les instabilites hydrodynamiques a l'interface de couches de cisaillement peuvent se produire selon differents modes et jouent un role important dans le mecanisme de mixage. Nous utilisons ici l'analyse de stabilite dans un cadre temporel afin d'etudier les caracteristiques de stabilite d'un ecoulement a deux couches stratifiees chargees de particules sur deux profils de densite de fond : doux (tangente hyperbolique) et lineaire par morceau. Nous considerons l'effet sur la stabilite de differents parametres, comme l'inclinaison du fond, la viscosite et la grosseur des particules. Nous utilisons la methode de collocation pseudospectrale qui emploie des polynomes de Chebyshev, pour resoudre deux equations aux valeurs propres couplees. Sur la base des resultats, les caracteristiques de stabilite sont differentes pour les deux profils de fond. Dans le cas R = 1(R est le rapport d'epaisseur entre le couche de cisaillement et celle de fond (densite), la frontiere de stabilite dans le profil doux est la transition du flot instable (ou le mode instable dominant est Kelvin-Helmholtz) au flot stable alors que dans le profil lineaire par morceaux cette frontiere est la transition du mode de Kelvin-Helmholtz au mode de Holmboe. Nous montrons aussi que la region instable croit avec la pente du fond et que les modes instables s'amplifient si cette pente augmente. Pour R = 5, le flot ne devient pas stable en augmentant la stratification pour une pente de fond non nulle et pour certains domaines du nombre d'onde, les modes de Kelvin-Helmholtz et de Holmboe cohabitent. De plus, une augmentation de la pente du fond cause des diminutions du taux de croissance du mode de Holmboe et de son domaine d'existence. Tel que prevu, la viscosite ameliore la stabilite du courant et pour de grandes valeurs de la viscosite (faible nombre de Reynolds) l'ecoulement devient stable aux grandes longueur d'onde (faible nombre d'onde) pour toutes les valeurs du nombre de Richardson. La presence de petites particules n'affecte pas beaucoup les caracteristiques de l'instabilite, cependant les grosses particules rendent l'ecoulement plus instable. [Traduit par la Redaction], 1. Introduction Stratified shear flows are observed frequently in environmental and geophysical flows. Atmospheric or oceanographic gravity currents are types of stratified shear flows. They appear as a result of [...]

Turbidity currents containing kaolin particles were studied experimentally in a channel and the velocity and concentration profiles were measured using an acoustic Doppler velocimeter. These experiments were performed to investigate the depositional behaviour of turbidity currents. The suspended sediment flux was evaluated by experimental and analytical methods and the results of these two methods were in a good agreement. To evaluate the suspended sediment flux, it was necessary to recognize the suspended sediment zone from the upper shear layer region and near the bed depositional area as well. The method of determination of these areas is discussed. The effects of important parameters including the inlet Froude number and bed slope were also studied. Based on these results, it can be concluded that the non-dimensional sediment flux decreases at the vicinity of the hydraulic jump with the inlet Froude number, whereas an increase in the bed slope reduces the non-dimensional sediment flux. [ABSTRACT FROM AUTHOR]