Combined Immersed Boundary/Large-Eddy-Simulations of Incompressible Three Dimensional Complex Flows

Cristallo, A.; Verzicco, Roberto

doi:10.1007/s10494-006-9034-6

Cited by 68 publications

(37 citation statements)

References 51 publications

(81 reference statements)

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“…to satisfy boundary conditions). In addition to the no-slip boundary condition for velocity, in practice, a wall stress model based on the equilibrium stress balance assumption or the Monin-Obukhov similarity theory is usually adopted when applying IBM to LES [20][21][22], due to impractical refinement of the whole regular grid in order to resolve the near-wall region, and the lack of an accurate wall model applicable for rough surfaces [23]. However, implementation of such a wall model in the context of IBM is not as straightforward as in TFCT due to the fact that an immersed boundary in IBM is generally not co-located with a grid line, and commonly used approaches such as smearing and linear interpolation [11,21] could introduce non-negligible errors.…”

Section: Introductionmentioning

confidence: 99%

Intercomparison of terrain-following coordinate transformation and immersed boundary methods in large-eddy simulation of wind fields over complex terrain

Fang

Porté‐Agel

2016

J. Phys.: Conf. Ser.

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Abstract. Accurate modeling of complex terrain, especially steep terrain, in the simulation of wind fields remains a challenge. It is well known that the terrain-following coordinate transformation method (TFCT) generally used in atmospheric flow simulations is restricted to non-steep terrain with slope angles less than 45 degrees. Due to the advantage of keeping the basic computational grids and numerical schemes unchanged, the immersed boundary method (IBM) has been widely implemented in various numerical codes to handle arbitrary domain geometry including steep terrain. However, IBM could introduce considerable implementation errors in wall modeling through various interpolations because an immersed boundary is generally not co-located with a grid line. In this paper, we perform an intercomparison of TFCT and IBM in large-eddy simulation of a turbulent wind field over a three-dimensional (3D) hill for the purpose of evaluating the implementation errors in IBM. The slopes of the three-dimensional hill are not steep and, therefore, TFCT can be applied. Since TFCT is free from interpolation-induced implementation errors in wall modeling, its results can serve as a reference for the evaluation so that the influence of errors from wall models themselves can be excluded. For TFCT, a new algorithm for solving the pressure Poisson equation in the transformed coordinate system is proposed and first validated for a laminar flow over periodic two-dimensional hills by comparing with a benchmark solution. For the turbulent flow over the 3D hill, the wind-tunnel measurements used for validation contain both vertical and horizontal profiles of mean velocities and variances, thus allowing an in-depth comparison of the numerical models. In this case, TFCT is expected to be preferable to IBM. This is confirmed by the presented results of comparison. It is shown that the implementation errors in IBM lead to large discrepancies between the results obtained by TFCT and IBM near the surface. The effects of different schemes used to implement wall boundary conditions in IBM are studied. The source of errors and possible ways to improve the IBM implementation are discussed.

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Section: Introductionmentioning

confidence: 99%

Intercomparison of terrain-following coordinate transformation and immersed boundary methods in large-eddy simulation of wind fields over complex terrain

Fang

Porté‐Agel

2016

J. Phys.: Conf. Ser.

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“…The fractional-step method is used with a three-step Runge-Kutta predictor to approximate convective and diffusive terms. 34 The solution of a Poisson pressure-correction equation using a multi-grid method is adopted as a corrector at the final step. Hydro3D has been validated in a series of hydroenvironmental engineering related problems, such as the flow in compound channels 35 and tidal steam turbines.…”

Section: A Numerical Frameworkmentioning

confidence: 99%

Large-eddy simulation of shallow turbulent wakes behind a conical island

et al. 2017

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Large-Eddy Simulations (LESs) and experiments were employed to study the influence of water depth on the hydrodynamics in the wake of a conical island for emergent, shallow, and deeply submerged conditions. The Reynolds numbers based on the island’s base diameter for these conditions range from 6500 to 8125. LES results from the two shallower conditions were validated against experimental measurements from an open channel flume and captured the characteristic flow structures around the cone, including the attached recirculation region, vortex shedding, and separated shear layers. The wake was impacted by the transition from emergent to shallow submerged flow conditions with more subtle changes in time-averaged velocity and instantaneous flow structures when the submergence increases further. Despite differences in the breakdown of the separated shear layers, vortex shedding, and the upward flow region on the leeward face (once the cone’s apex is submerged), similar flow structures to cylinder flow were observed. These include an arch vortex tilted in the downstream direction and von Karman vortices in the far-wake. Spectra of velocity time series and the drag coefficient indicated that the vortex shedding was constrained by the overtopping flow layer, and thus the shedding frequency decreased as the cone’s apex became submerged. Finally, the generalised flow structures in the wake of a submerged conical body are outlined.

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“…The main advantage of using the IB consists in solving flows bounded by arbitrarily complex geometries without resorting to body-conformal grids for which the motion is prescribed, and, therefore, the solution technique essentially has the same ease of use and efficiency as that of simple geometries. The method is second-order in space and this technique has already been implemented in many different scenarios and grid layouts, e.g., laminar and turbulent convection, 27-29 turbulent flows and particle collision, [30][31][32][33] biological devices, 34 and bifurcations. 35 The threedimensional simulations were conducted using the immersed boundary method of Ref.…”

Section: Numerical Scheme and The Experimental Setupmentioning

confidence: 99%

Fluid velocity fluctuations in a collision of a sphere with a wall

et al. 2011

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A study of thermal counterflow using particle tracking velocimetry Phys. Fluids 23, 107102 (2011) Particle accumulation on periodic orbits by repeated free surface collisions Phys. Fluids 23, 072106 (2011) We report on the results of a combined experimental and numerical study on the fluid motion generated by the controlled approach and arrest of a solid sphere moving towards a solid wall at moderate Reynolds number. The experiments are performed in a small tank filled with water for a range of Reynolds numbers for which the flow remains axisymmetric. The fluid agitation of the fluid related to the kinetic energy is obtained as function of time in the experiment in a volume located around the impact point. The same quantities are obtained from the numerical simulations for the same volume of integration as in the experiments and also for the entire volume of the container. As shown in previous studies, this flow is characterized by a vortex ring, initially in the wake of the sphere, that spreads radially along the wall, generating secondary vorticity of opposite sign at the sphere surface and wall. It is also observed that before the impact, the kinetic energy increases sharply for a small period of time and then decreases gradually as the fluid motion dies out. The measure of the relative agitation of the collision is found to increase weakly with the Reynolds number Re. The close agreement between the numerics and experiments is indicative of the robustness of the results. These results may be useful in light of a potential modelling of particle-laden flows. Movies illustrating the spatio-temporal dynamics are provided with the online version of this paper.

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Combined Immersed Boundary/Large-Eddy-Simulations of Incompressible Three Dimensional Complex Flows

Cited by 68 publications

References 51 publications

Intercomparison of terrain-following coordinate transformation and immersed boundary methods in large-eddy simulation of wind fields over complex terrain

Intercomparison of terrain-following coordinate transformation and immersed boundary methods in large-eddy simulation of wind fields over complex terrain

Large-eddy simulation of shallow turbulent wakes behind a conical island

Fluid velocity fluctuations in a collision of a sphere with a wall

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