A model predictive wind farm controller with linear parameter-varying models

In this paper, we present an implementation of a model predictive controller (MPC) for wind farm power tracking problem. The controller is evaluated in the high-fidelity PAral-lelized Large-eddy simulation Model (PALM). By taking measurements from PALM, we show that the closed-loop MPC can provide power reference tracking while reducing force...

Fully compressible low-Mach number simulations of carbon-dioxide at supercritical pressures and trans-critical temperatures

This work investigates fully developed turbulent flows of carbon-dioxide close to its vapour-liquid critical point in a channel with a hot and a cold wall. Two direct numerical simulations are performed at low Mach numbers, with the trans-critical transition near the channel centre and the cold wall, respectively. An additional simulation...

Turbulence attenuation in simultaneously heated and cooled annular flows at supercritical pressure

Heated or cooled fluids at supercritical pressure show large variations in thermophysical properties, such as the density, dynamic viscosity and molecular Prandtl number, which strongly influence turbulence characteristics. To investigate this, direct numerical simulations were performed of a turbulent flow at supercritical pressure (CO2 at 8...

Numerical simulation of turbulent heat transfer close to the critical point

In this paper we discuss the effect of sharp property variations on the turbulent heat transfer in fluids close the critical point. The governing equations for this flow regime are discussed, a short description of the numerical tools that have been developed to study these flows is given. Finally, some results for supercritical heat transfer in...

Large-eddy simulation of highly underexpanded transient gas jets

Large-eddy simulations (LES) based on scale-selective implicit filtering are carried out in order to study the effect of nozzle pressure ratios on the characteristics of highly underexpanded jets. Pressure ratios ranging from 4.5 to 8.5 with Reynolds numbers of the order 75?000–140?000 are considered. The studied configuration agrees well with...

Experiments on the Flow Field and Acoustic Properties of a Mach number 0·75 Turbulent Air Jet at a Low Reynolds Number

In this paper we present the experimental results of a detailed investigation of the flow and acoustic properties of a turbulent jet with Mach number 0·75 and Reynolds number 3·5 103. We describe the methods and experimental procedures followed during the measurements, and subsequently present the flow field and acoustic field. The experiment...

The stress generated by non-Brownian fibers in turbulent channel flow simulations

Turbulent fiber suspension channel flow is studied using direct numerical simulation. The effect of the fibers on the fluid mechanics is governed by a stress tensor, involving the distribution of fiber position and orientation. Properties of this function in channel flow are studied by computing the trajectories and orientations of individual...

On the performance of the moment approximation for the numerical computation of fiber stress in turbulent channel flow

Fiber-induced drag reduction can be studied in great detail by means of direct numerical simulation [ J. S. Paschkewitz et al., J. Fluid Mech. 518, 281 (2004) ]. To account for the effect of the fibers, the Navier-Stokes equations are supplemented by the fiber stress tensor, which depends on the distribution function of fiber orientation angles....

Events of high polymer activity in drag reducing flows

Low dissipative methods for turbulent reacting flows

Modeling of scalar transport is an essential point in the simulation of non-premixed turbulent combustion. The fuel and oxidizer streams are, in general, modeled with an equation for the mixture fraction Z. This mixture fraction is a bounded function, i.e. it can never become large than one or smaller than zero. Symmetric central differencing...

Low dissipative methods for turbulent reacting flows

Modeling of scalar transport is an essential point in the simulation of non-premixed turbulent combustion. The fuel and oxidizer streams are, in general, modeled with an equation for the mixture fraction $Z$. This mixture fraction is a bounded function, i.e. it can never become large than one or smaller than zero. Symmetric central differencing...

Direct numerical simulations of turbulent flow over a permeable wall using a direct and a continuum approach

A direct numerical simulation (DNS) has been performed of turbulent channel flow over a three-dimensional Cartesian grid of 30×20×9 cubes in, respectively, the streamwise, spanwise, and wall-normal direction. The grid of cubes mimics a permeable wall with a porosity of 0.875. The flow field is resolved with 600×400×400 mesh points. To enforce...

Local grid refinement in large-eddy simulations. Large-scale numerical modelling of problems involving the Navier-Stokes equations