Mike by dhi 2014 mike 21 flow model fm parallelisation using gpu. Mike 21 flow model is applicable to the simulation of hydraulic and environmental phenomena in lakes, estuaries, bays, coastal areas and seas. The eddy viscosity is also commonly called the turbulent viscosity and it is normally written as. Pdf wave breaking simulation by a boussinesq model in two. Linear eddyviscosity models 201112 9 38 zeroequation models. The moving fluid creates a space devoid of downstreamflowing fluid on the downstream side of the object. Mike 21 spectral wave module 2005, scientific documentation, dhi software. The objective is to provide the user with a detailed description of the flow and transport model equations, numerical discretization and solution methods. Coming to the eddy viscosity submenu we select constant value and flux based.
Eddy viscosity is a function of the flow, not of the fluid. Turbulent flows are commonplace in most real life scenarios, including the flow of blood through the cardiovascular system, the airflow over an aircraft wing, the reentry of space vehicles, besides others. Creating the input parameters for the mike 21 flow model fm simulation. Eggers lctngzey research center langzey station, humpton, va. Estimation of oceanic eddy viscosity profile and wind stress. Eddy viscosity is often represented by the symbol k, and the turbulence parameterization that uses eddy viscosity is called ktheory. The classic version of mike 21 uses a rectangular grid and solves the shallow water equations by means of a finite difference scheme.
Five groups of experiments are designed to investigate the influences that the optimization algorithms, steplength, inverse integral time of the adjoint model, prescribed vertical distribution of eddy viscosity, and regularization parameter exert on the. In the nearshore environment, large mixing or turbulence occurs due to waves, wind, bottom. The results of this study showed that mike21 results were. We can also define a kinematic turbulent viscosity. The hydrodynamic hd module is the basic module in the mike 21 flow model. Given appropriate initial conditions, the mike 21 classic can be used to efficiently simulate the propagation of tsunamis generated by both earthquakes and submarine slumps. Mike by dhi software is the result of years of experience and dedicated. The eddy viscosity depends on the fluid density and distance from the river bed or ground surface. Turbulence modeling is the construction and use of a mathematical model to predict the effects of turbulence. Linear eddyviscosity models university of manchester. For the parabolic model, the eddy viscosity is calculated as. Eddy viscosity and diffusivity modeling sciencedirect. Two parameters were analysed during the model calibration. The region of rapid change in \barv can be identified as the logarithmic region.
The fundamentals for the eddyviscosity models are discussed, including the boussinesq hypothesis, the derivation of. Modelling tsunamis generated by earthquakes and submarine slumps using mike 21 stephen anton luger, rhydar lee harris. The fundamentals for the eddyviscosity models are discussed, including the boussinesq hypothesis, the derivation of the lawofthewall and. Fluid behind the obstacle flows into the void creating a swirl of fluid on each edge of the obstacle, followed by a short reverse flow of fluid behind the. The spatial discretization of the equations in the mike 21 fm and delft3d fm models, which adopt unstructured grids, is performed using a cellcentred finite volume method dhi 2014a. Depending on the amount and quality of the data sets this can be a. The first parameter to be analysed was the eddy viscosity. Modeling sensitivity using constant eddy viscosity and. Mike 21 flow model, hydrodynamic module, user guide. The mike 2 coupled model fm was calibrated versus field measurement data. The rate of transfer of a conservative fluid property through a surface by turbulent eddies. The manual provides an introduction to srh2d, its unique capability and its potential applications.
In eddy viscosity turbulence models the reynolds stresses are linked to the velocity gradients via the turbulent viscosity. Estimation of oceanic eddy viscosity profile and wind. The eddy viscosity or ktheory approach is a parameterization for the eddy momentum flux reynolds stress that works reasonably well when only small eddies are present in the flow, but that behaves poorly when large eddy coherent. In order to describe the turbulence contribution from jet interaction, the eddy viscosity suggested by prandtl has. The horizontal eddy viscosity type has been chosen to a flux based sma gorinsky. Dec 14, 2015 hecras solves the full 2d shallow water equations, including coriolis effects and representation of horizontal turbulent dispersion of momentum using an eddy viscosity approach. Mike by dhi software is the result of years of experience and dedicated development and has, in many regions, become the standard modelling tool. This report makes a thoroughly analysis of the twoequation eddyviscosity models evms. Is it only about the resolution accuracy of turbulence and eddy calculations. For these models the time integration of the shallow water equations is performed using an. A short presentation of other types of cfdmodels is also included. Prestedge retief dresner wijnberg, 5th floor, safmarine quay, clock tower.
Firstly we will use mike 21 to set up the model and we will try to couple with mike 11 to run a precise simulation. The user only has to define the minimum and maximum time step, as well. Mathematical formulation, numerical methods, and solution algorithms are presented. Wave breaking simulation by a boussinesq model in two horizontal dimensions. I the linear eddyviscosity formulation is thus relatively e asy to implement, and is generally fairly stable, since the turbulent viscosi ty related diffusion terms can mostly be treated in an implicit manner. Flood modeling for risk evaluation a mike flood vs. Modeling sensitivity using constant eddy viscosity and zero. Thus, the model consists of continuity, momentum, temperature, salinity and density equations and it is closed by a turbulent closure scheme. The turbulence is modelled using an eddy viscosity concept.
Therefore, the eddy viscosity is an important parameter which can have a large influence on the calculated flow field and resulting sediment transport. For details please refer to your dhi software licence. Replicating mike 21 results 2d domains tuflow forum. Review and cite mike software protocol, troubleshooting and other. This document refers to proprietary computer software, which is. Hydrodynamic and transport module short description. Nov 10, 2008 there is an area downstream of the bridges where the tuflow model consistently for viscosity formulations constant, smagorinsky and a combination of both, for a range of viscosities from 0. There was some discussion that some 2d models actually solve the 1d form of the shallow water equations on a 2d mesh. Velocity profiles and eddy viscosity distributions.
One purpose of the present report was to validate or disprove recent formulations for the eddy viscosity function, and another purpose was to establish whether or not experimental determination of eddy viscosity distributions is feasible. Velocity profiles and eddy viscosity distributions downstream. The mt module includes a stateoftheart mud transport model that simulates the erosion. It was found to be suited for well mixed systems like hoogly estuary niot 2004. Eddy viscosity is generally found to have an insignificant influence on these. The horizontal eddy viscosity type has been set to a velocity based smagorinsky formulation with a constant value of 0. Mike 21 flow model is a modeling system for 2d freesurface flows. Cabot 2 a general discussion on the structure of the eddy viscosity tensor in anisotropic flows is presented. Also model validation is discussed in this document. Mike 21 graphical processing units gpu verification report.
A e b t, \displaystyle \mu aebt, 2 where a \displaystyle a and b. The derivation of a turbulent eddy viscosity model begins with the spectral energy balance equation. A low value is associated with \ \barv 1 \ where viscous stresses dominate turbulent stresses, and a high value where turbulent stresses are dominant. The eddy viscosity is intended to simulate the dissipation of energy at smaller scales than the model can simulate. Adjoint method is used to assimilate pseudoobservations to simultaneously estimate the oevp and the wsdc in an oceanic ekman layer model. There is an area downstream of the bridges where the tuflow model consistently for viscosity formulations constant, smagorinsky and a combination of both, for a range of viscosities from 0. This result has the same form as the widespread and accurate empirical relation. Applicability of mike 21 to assess temporal and spatial. Eddy viscosity article about eddy viscosity by the free. Modelling tsunamis generated by earthquakes and submarine.
Including the mike 21 flow model fm twodimensional flow and mike 3 flow model fm three dimensional flow. Mike 21 flow model is a modelling system for 2d freesurface flows. It may be applied wherever stratification can be neglected. The term eddy viscosity arises from the fact that smallscale vortices or eddies on the order of the grid cell size are not resolved, and only the largescale flow is simulated. This report serves as the theory and users manual for srh2d v2. It transforms our science into practice and gives you the competitive edge and, through the dhi academy, you can rest assured that there is a local team of highly skilled experts committed to train.
Pdf assessment of mike21 model in dam and dikebreak simulation. The systematic use of tensor symmetries and flow symmetries is shown to reduce drastically the number of independent parameters needed to describe the rank 4 eddy viscosity tensor. The value of the coefficient of eddy viscosity an exchange coefficient is of the order of 1 m 2 s1, or one hundred thousand times the molecular kinematic viscosity. Mike 21 flow model fm sand transport module river application. Pdf wave breaking simulation by a boussinesq model in. The eddy viscosity affects the transverse distribution of the flow velocity, so it is mainly. Mike21 is a good choice for your interest, we used it in the simulation of tide and. Its unit is the same as that of the molecular viscosity.
The lack of geographical coordinates in mike 21 classic can however result in a distorted grid when simulating larger domains. Hecras solves the full 2d shallow water equations, including coriolis effects and representation of horizontal turbulent dispersion of momentum using an eddy viscosity approach. Also, the turbulent transfer of water vapor may be expressed in energy units by. Twodimensional depthaveraged flow modeling with an. Link between eddy viscosity and subgridscale turbulent viscosity in les.
It is capable of handling flooding and drying, spatially varying surface roughness, eddy viscosity, coriolis forces and wind friction. Five groups of experiments are designed to investigate the influences that the optimization algorithms, steplength, inverse integral time of the adjoint model, prescribed vertical distribution of eddy viscosity, and regularization. Nita yuanita program studi teknik kelautan kamis, 10 september 2009 outline paramater dasar basic parameters parameter hidrodinamika hydrodynamics parameter umum basic parameter hydrodynamics parameter persamaan pengatur persamaan kontinuitas x, y space coordinates m t time s h x,y,t water depth m x,y,t surface elevation m p, q x,y,t flux. Unlike most models, mike 21 fm has a dynamic time step determined by the model in order to verify the cfl number. Turbulent eddy viscosity jhu center for imaging science. The hyptheses that the effect of turbulent eddies on the flow can be modeled in this was is often refered to as the boussinesq eddy viscosity assumption and it was first formulated by boussinesq in 1877.
Nita yuanita program studi teknik kelautan kamis, 10 september 2009 outline paramater dasar basic parameters parameter hidrodinamika hydrodynamics parameter umum basic parameter hydrodynamics parameter persamaan pengatur persamaan kontinuitas x, y space coordinates m t time s h x,y,t water depth. In cmsflow, the total eddy viscosity is equal to the sum of three parts. Channel bend loss all three software produce slightly different but consistent results. Lecture 10 turbulence models applied computational fluid. Twoequation eddyviscosity models are based on approximate constitutive equations which predict the unknown reynolds stress tensor that appears in the reynoldsaveraged navierstokes equations.