A Parallel Non-Staggered Navier-Stokes Solver Implemented on a Workstation Cluster

Armfield, S.W.; Morgan, Philip E.; Norris, Stuart; Street, Robert L.

doi:10.1007/978-3-642-59334-5_3

Cited by 20 publications

(12 citation statements)

References 10 publications

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“…Each component of the coupled solver system has previously been validated individually. A CFL number of 0.2 was shown to be sufficient to guarantee stability of the flow simulation. Turbulence spectra were examined for the flows presented, which indicated that at least 90% of the inertial sub‐range was being simulated.…”

Section: Resultsmentioning

confidence: 99%

“…The SnS CFD code was developed at The University of Sydney and The University of Auckland. The code uses a structured, non‐staggered mesh and a fractional step solver for modelling transient flows. The diffusive components of the momentum equations are discretized in space with the use of central differencing and in time with the use of the Crank–Nicolson scheme.…”

Section: Methodsmentioning

confidence: 99%

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Large eddy simulation of dynamically controlled wind turbines in an offshore environment

et al. 2012

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Accurate modelling of transient wind turbine wakes is an important component in the siting of turbines within wind farms because of wake structures that affect downwind turbine performance and loading. Many current industry tools for modelling these effects are limited to empirically derived predictions. A technique is described for coupling transient wind modelling with an aero-elastic simulation to dynamically model both turbine operation and wake structures. The important feature of this approach is a turbine model in a flow simulation, which actively responds to transient wind events through the inclusion of controller actions such as blade pitching and regulation of generator torque. The coupled nature of the aero-elastic/flow simulation also allows recording of load and control data, which permits the analysis of turbine interaction in multiple turbine systems. An aero-elastic turbine simulation code and a large eddy simulation (LES) solver using an actuator disc model were adapted for this work. Coupling of the codes was implemented with the use of a software framework to transfer data between simulations in a synchronous manner. A computationally efficient simulation was developed with the ability to model turbines exhibiting standard baseline control operating in an offshore environment. Single and multiple wind turbine instances were modelled in a transient flow domain to investigate wake structures and wake interaction effects. Blade loading data were analysed to quantify the increased fluctuating loads on downwind turbines. The results demonstrate the successful implementation of the coupled simulation and quantify the effect of the dynamic-turbine model.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Large eddy simulation of dynamically controlled wind turbines in an offshore environment

et al. 2012

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“…DNS The equations are solved using the fractional-step finite-volume solver described in Armfield et al (2002). The code uses a cell-centred co-located storage arrangement for flow variables on a regular structured grid, with cell-face velocities calculated using the Rhie-Chow momentum interpolation.…”

Section: Problem Formulationmentioning

confidence: 99%

Transition to stably stratified states in open channel flow with radiative surface heating

et al. 2015

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Direct numerical simulations (DNS) of turbulent stratified flow in an open channel with an internal heat source following the Beer-Lambert law from the surface are used to investigate the transition from neutral to strongly stable flow. Our buoyancy bulk parameter is defined through the ratio of the domain height δ to L , a bulk Obukhov length scale for the flow. We cover the range λ = δ/L = 0-2.0, from neutral conditions to the onset of the stable regime, with the Reynolds number range Re τ = 200-800, at a Prandtl number of 0.71. The result is a boundary layer flow where the effects of stratification are weak in the wall region but progressively stronger in the outer layer up to the free surface. At λ 1 the turbulent kinetic energy (TKE) budget is in local equilibrium over a region extending from the near-wall region to a free-surface affected region a distance l ν from the surface, with l ν /δ ∼ Re −1/2 . In this equilibrium region the flow can be characterised by the flux Richardson number R f and the local Obukhov length scale Λ. At higher λ local mixing limit conditions are observed over an extended region. At λ = 2 the flux Richardson number approaches critical limit values of R f ,c 0.18 and gradient Richardson number Ri c 0.2. At high λ, we obtain a flow field where buoyancy interacts with the smallest scales of motion and the turbulent shear stress and buoyancy flux are suppressed to molecular levels. We find that this regime can be identified in terms of the parameter Re L ,c = L u τ /ν 200-400 (where u τ is the friction velocity and ν the kinematic viscosity), which is related to the L * parameter of Flores and Riley (Boundary-Layer Meteorol., vol. 139 (2), 2011, pp. 241-259) and buoyancy Reynolds number R. With energetic equilibrium attained, the local buoyancy Reynolds number, Re Λ = Λ u w 1/2 /ν, is directly related to the separation of the Ozmidov (l O ) and Kolmogorov (η) length scales in the outer boundary layer by Re Λ R ≡ (l O /η) 4/3 . The inner wall region has the behaviour R ∼ Re L Re τ , in contrast to stratified boundary layer flows where the buoyancy flux is non-zero at the wall and R ∼ Re L .

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“…The computations presented in this work were conducted using SnS, a CFD code developed at the Universities of Auckland and Sydney , . The code models transient flows using a structured, non‐staggered Cartesian mesh using a fractional step solver .…”

Section: Numerical Methodologymentioning

confidence: 99%

An actuator sector method for efficient transient wind turbine simulation

2014

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This paper investigates a new method for transient simulation of flow through a wind turbine using an actuator technique. The aim, in the context of wind turbine wake simulation, is to develop an alternative to the widely used actuator disc model with an increased resolution and range of applications, for the same or less computational expense. In this new model, the actuator sector method, forces applied to the fluid are distributed azimuthally to maintain a continuous flow solution for increased time-step intervals compared with the actuator line method. Actuator sector results are presented in comparison with actuator disc and actuator line models initially for a non-dimensionalized turbine in laminar onset flow. Subsequent results are presented for a turbine operating in a turbulent atmospheric boundary layer. Results show significant increases in flow fidelity compared with actuator disc model results; this includes the resolution of diametric variation in rotor loading caused by horizontal or vertical wind shear and the helical vortex system shed from the turbine blade tips. Significant reductions in computational processing time were achieved with wake velocities and turbulence statistics comparable with actuator line model results. The actuator sector method offers an improved alternative to applications employing conventional actuator disc models, with little or no additional computational cost. This technique in conjunction with a Cartesian mesh-based parallel flow solver leads to efficient simulation of turbines in atmospheric boundary layer flows.

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A Parallel Non-Staggered Navier-Stokes Solver Implemented on a Workstation Cluster

Cited by 20 publications

References 10 publications

Large eddy simulation of dynamically controlled wind turbines in an offshore environment

Large eddy simulation of dynamically controlled wind turbines in an offshore environment

Transition to stably stratified states in open channel flow with radiative surface heating

An actuator sector method for efficient transient wind turbine simulation

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