China
Africa
Explore chapters and articles related to this topic
CFD modelling of HAM transport in buildings: Boundary conditions
Published in Paul Fazio, Hua Ge, Jiwu Rao, Guylaine Desmarais, Research in Building Physics and Building Engineering, 2020
H.-J. Steeman, C. T’Joen, A. Willockx, M. De Paepe, A. Janssens
Simulation of a wall-bounded turbulent flow requires an appropriate description of the flow in the near wall region. The realizable k-epsilon turbulence model is only valid for flow far away from the walls (high Reynolds number). The flow near the wall can be modelled in Fluent using wall functions or two-layer zonal models. The wall functions included in Fluent cannot be used in the test cases presented in this article since they are created for forced convection and are not valid for natural convection (Fluent Inc. 2003). Unlike the wall functions the two-layer model is applicable for as well forced as natural convection. For this reason the latter model is used.
Modelling and Optimization of a Fuel Tank for Reduction of Sloshing Effect
Published in Rajesh Singh, Anita Gehlot, P.S. Ranjit, Dolly Sharma, Futuristic Sustainable Energy and Technology, 2022
Alok Kumar Mishra, Ujjal Kalita, Manminder Singh Malhi, Santosh Kumar Behera, Shahid Khan, Twisampati Roy Chowdhury
The principle of the turbulence models has changed. The principle that k-epsilon turbulence model works on focuses on the mechanisms that affect the turbulent kinetic energy, unlike earlier models of turbulence. The assumption related with this model is isotropic (uniform in all orientations) or it is having the ratio between Reynolds’s stress and mean rate of deformations same in each and every direction. [13]
Numerical simulations of a swimmer’s head and cap wearing different types of goggles
Published in Sports Biomechanics, 2021
Daniel A. Marinho, Dennis Willemsen, Tiago M. Barbosa, António José Silva, J. Paulo Vilas-Boas, Henrique P. Neiva, Pedro Forte
All CFD simulations were run with 3D double-precision settings. For the near-wall treatment, non-equilibrium wall functions were selected (Forte et al., 2018). These give improved predictions for fluid flows in the case of strong separation and large adverse pressure gradients compared to the standard wall-functions (Bakker, 2006). For the turbulence modelling, the viscous Realizable k-epsilon model was selected. The k-epsilon turbulence model is a 2-equation model with good predictions for turbulent flows. The model has been used successfully and extensively for industrial applications (Raiesi et al., 2011) and has shown good accuracy in modelling human swimming (Bixler et al., 2007; Bixler & Riewald, 2002; Moreira et al., 2006).
A detailed modelling on spray atomisation and combustion of LOX/GCH4 in variable area pintle injector rocket engines
Published in Combustion Theory and Modelling, 2021
Kanmaniraja Radhakrishnan, Keonwoong Lee, Jaye Koo
The next step is modelling-3 in Figure 3. The simulation model for performing the spray combustion is shown in Figure 2(c). The dimensions of the chamber length, chamber diameter, nozzle throat diameter, nozzle exit diameter, nozzle convergent length, and nozzle divergent length were 60, 56, 13.3, 42.4, 31 and 29 mm, respectively. The gaseous methane at 300 K was injected from an annular gap while liquid oxygen as a droplet size expressed in terms of Rosin–Rammler distribution at 85 K was injected at the exit of a centre gap of the pintle injector. The gaseous methane was treated as a continuum field and solved by RANS equations whereas the liquid drop of LOX was considered as a discrete phase and solved using the Lagrangian approach by employing the stochastic tracking method. The standard K-epsilon turbulence model was applied with a standard wall function. A steady diffusion flamelet (SDF) [33–38] library for non-adiabatic flow was created using GRI 3.0 CHEMKIN file that has been used to generate the flamelet table to calculate the chemistry inside the combustion chamber. In the flamelet generated table, the temperature, density and species as a function of mean mixture fraction, mixture fraction variance, enthalpy, and scalar dissipation were constructed. The diffusion flamelets over a strain rate is determined for a specified scalar dissipation rate as, where the value is from 1 to 10 as a maximum number of diffusion flamelets taken into account wherein the initial scalar dissipation, and scalar dissipation step, are 0.01 and 5 s−1, respectively.
Numerical and experimental investigation of the effect of moonpool positioning on the hydrodynamics of floating drilling production storage and offloading vessel
Published in Ships and Offshore Structures, 2022
Abhishek Yadav, V. Anantha Subramanian, P. Ananthakrishnan
Modelling limitations result from the necessity to describe the flow phenomena such as turbulence, and multi-phase flows by empirical models. The present study uses the K-epsilon turbulence model. ITTC recommended procedure and guidelines have been followed for standardisation and to minimise inaccuracies. The grid dependency test performed helps to achieve faster convergence with efficient computational time. Inaccuracy in hydrodynamic drag estimation has a best value within 2%.