Hassan I. Kassem

Fraunhofer Institute for Wind Energy Systems IWES | IWES · Department of Aerodynamics and Numerical Wind Energy Meteorology

This work discusses the implementation of eddy dissipation model in OpenFOAM CFD toolbox. The code was validated in modeling of confined non-premixed Methane jet flame. The model predictions were extensively compared against published experimental results as well as ANSYS Fluent® predictions. The differences between the implemented model in OpenFOA...

This paper focuses on the coupling between a high fidelity aerodynamic model for the flow field and a relatively low fidelity model for modal analysis of the structure of a cantilever wing. This coupled aeroelastic model is implemented in one of the widely used open source computational fluid dynamics code called OpenFOAM. The methodology is develo...

Free vibration and flutter analyses of two types of high aspect ratio aircraft wings are presented. The wing is idealised as an assembly of bending-torsion coupled beams using the dynamic stiffness method leading to a nonlinear eigenvalue problem. This problem is solved using the Wattrick-Williams algorithm yielding natural frequencies and mode sha...

Prediction of the boundary layer transition from laminar to turbulent is essential for accurately calculating the aerodynamic forces on airfoils. Yet, it is still a challenging task for most RANS turbulence models (Reynolds-averaged Navier–Stokes) which are build on a fundamental assumption that the flow is fully turbulent. Although there are some...

A variety of airfoils designed for wind turbine rotor blade applications were simulated with k − ω shear stress transport (SST) turbulence model in its standard form, the k − ω SST turbulence model with a modified a 1 constant (referred to as the a 1 method), the Spalart-Allmaras turbulence model, and the panel method XFoil. To assess their perform...

Gaussian and intermittent synthetically generated turbulences are investigated as initial conditions for high-resolution numerical simulations. Turbulent fields, namely the Mann and the intermittent Time-mapped Mann model, are injected into large eddy simulations, and subsequently their convergences are investigated. In addition to the usual one-po...

One of the challenges in digitizing the wind energy sector is to have reliable, accurate and efficient data assessment and prediction tools. We believe that accurate surrogates are key towards improving efficiency and reliability for informed decision making. For a quantitative understanding of wind and energy in complex terrains, a detailed site a...

A new approach to derive a synthetic wind field model which combines spatial correlations from the Mann model and intermittency is introduced. The term intermittency describes the transition from Gaussian to non-Gaussian velocity increment statistics at small scales, where non-Gaussian velocity increment statistics imply a higher probability for ex...

One of the emerging problems in modern computational fluid dynamics is the simulation of flow over rough surfaces. A good example of these rough surfaces is wind turbine blades with ice formation on its leading edge. Instead of resolving the airflow field using a fine computational grid near the wall, rough wall functions (RWFs) can be used to mode...

A new approach to derive a synthetic wind field model which combines spatial correlations from the Mann model and intermittency is introduced. The term intermittency describes the transition from Gaussian to non-Gaussian velocity increment statistics at small scales, where non-Gaussian velocity increment statistics imply a higher probability for ex...

The planning and realization of wind energy projects requires an as accurate and precise wind resource estimation as possible. Standard procedures combine shorter on-site measurements with the application of numerical models. The uncertainties of the numerical data generated from these models are, particularly in complex onshore terrain, not just r...

The numerical wind resource assessment has become an essential tool for siting engineers and nonlinear models, such as CFD, are now being used on a daily basis. However, due to the uncertainty associated with the measurements and the topological data, the user typically has to calibrate the model input parameters to match the measured situations. T...

In wind energy site assessment, one major challenge is to represent both the local characteristics as well as general representation of the wind climate on site. Micro-scale models (e.g., Reynolds-Averaged-Navier-Stokes (RANS)) excel in the former, while meso-scale models (e.g., Weather Research and Forecasting (WRF)) in the latter. This paper pres...

One of the emerging problems in modern computational fluid dynamics is the simulation of flow over rough surfaces, wind turbine blades with ice on its surface for instance. An alternative method to numerically simulate rough surfaces instead of using a grid with y+

A continuous adjoint solver is developed for calibration of the inlet velocity profile boundary condition (BC) for computational fluid dynamics (CFD) simulations of the neutral atmospheric boundary layer (ABL). The adjoint solver uses interior domain wind speed observations to compute the gradient of a calibration function with respect to inlet vel...

The use of stochastic analysis enables a theoretically well based, systematic derivation of a probability density function (PDF)-realizable dynamic LES model. However, this PDF-realizable model is not always stable due to the rare appearances of non-realizable SGS stress values. The stability of dynamic simulations is found to be a difficult challe...

A continuous adjoint solver is developed for optimization of the inlet velocity profile boundary condition for CFD simulations of the neutral atmospheric boundary layer (ABL). The adjoint solver uses interior domain wind speed observations to compute the gradient of a calibration function with respect to inlet velocity components and wind direction...

To describe the combustion process in the burners with complicated configuration used in the industrial applications, a non-adiabatic three-stream flamelet/progress variable (FPV) model for simulating pulverized coal combustion (PCC) is proposed in the context of large eddy simulation (LES). A conserved scalar associated with oxidizer split is intr...

In this presentation, a fluid-structure interaction (FSI) framework for aeroelastic stability analysis will be presented, namely transonic flutter. Avoiding flutter is a mandatory requirement in any aircraft design process. Although flutter analysis is a relatively old problem in aviation, but it is still challenging, particularly with the advent o...

In this article, we present three dimensional CFD study of turbulent vortex flow in an annular passage using OpenFOAM 1.6. The vortex flow is generated by introducing the flow through a tangential entry to the passage. For the analysis presented in this article, turbulence was modeled using the . R ε/. k-. ε model, in addition, a comparison between...

The chemical reaction rate is highly dependent on the turbulence time scale in the eddy-dissipation model of diffusion flames. In the present work, two turbulence time scales and their effect on the flame predictions are investigated. The first time scale is the large eddy time scale based on the ratio between turbulence dissipation rate and kineti...

Two turbulence models were used to comparatively predict the isothermal flow field of Sydney swirling flame. The emphasis of the present work is on the predictability of the forced vortex flow field of each turbulence model. The ε ε − k R / eddy viscosity turbulence model was used in comparison with the Launder, Reece and Rodi (LRR) Reynolds stress...

In this paper, a new variant of the k-ε turbulence model (Saqr et al., CFD Letters, 1(2) pp. 87–94) is used to compute the shear driven vortex flow in an open cylindrical cavity. The results are compared with published LDA measurements for such flow configuration. The modified turbulence model demonstrated good agreement with experimental results,...

This article reports the ideal detonation characteristics of various mixtures of biogas-hydrogen and biogas-hydrogen peroxide with air. The results obtained by the chemical equilibrium calculations reveal the fundamental improvement of the biogas detonation characteristics when it is mixed with either H2 or H2O2. However, a discussion is conducted...

We present the results of a time-dependent three-dimensional numerical simulation of the turbulent mixing characteristics in the mixing chamber of a hypersonic pulse detonation engine (PDE). Fuel (C 3 H 8) was injected through one supersonic injector, while the oxidizer (O 2) were injected through four supersonic injectors. The spatial distribution...

In this paper, we assess the performance of four RANS turbulence models in computing the averaged flow field through a curved duct. The Models studied are the standard k-ɛ, the standard k-ω, The Reynolds Stress Model, and the v2f model. Although the four models showed similar quantitative agreement for the tangential velocity profile with experimen...

Large Eddy Simulation (LES) of the two dimensional shear-driven flow in a cylindrical cavity has been performed to shed the light on the dynamics of the vortex core. Four different Reynolds numbers were considered in the present analysis. The time averaged velocity profiles inside the cavity showed excellent agreement with published LDA measurement...

This work discusses the implementation of eddy dissipation model in OpenFOAM CFD toolbox. The code was validated in modeling of confined non-premixed Methane jet flame. The model predictions were extensively compared against published experimental results as well as ANSYS Fluent® predictions. The differences between the implemented model in OpenFOA...

Using baffles in exhaust mufflers is known to improve their transmission loss. The baffle cut ratio should affect the muffler performance analogous to a shell-and-tube heat exchanger. To the authors’ knowledge, there is no previous assessment reported in literature of the effects that the baffle cut ratio configuration has on acoustic response and...