Showing 4 results for Flat Plate
Vahid Esfahanian, Ali Akbar Dehghan, Khoshab Masih, Hossain Chizari,
Volume 15, Issue 3 (5-2015)
Abstract
Transition control is of the great significance in laminar flows since determination of aerodynamics coefficients as well as heat transfer magnitude is strongly affected by accurate prediction and control of this phenomenon. Transition is severely dependent on space and time such that various microscopic and macroscopic scales can convert to each other rapidly. In one side, available uncertainties in RANS turbulence models can lead to inappropriate, or at least expensive, designs. In the other side, considering the growing rate of computational resources along with development of more efficient numerical methods in CFD applications, Direct Numerical Simulation, DNS, has found an applicable role even in industrial applications. In present study, a robust computational code is developed for Direct Numerical Simulation aimed at fundamental purposes. To this end, high-order compact finite-difference for spatial derivatives and high-order Runge-Kutta time integration are used in the present code as well as a low-pass filter to elucidate spurious oscillations. Also, non-reflecting boundary condition is employed to keep the domain size as small as possible and to improve the numerical accuracy at the boundaries. In present study, Direct Numerical Simulation investigates controlled transition scenarios for flow over a flat plate. Results are in a good agreement with those of previous researches both qualitatively and quantitatively which verify the various parts of the developed solver.
Mojtaba Kazemi Kelishami, Esmail Lakzian,
Volume 16, Issue 4 (6-2016)
Abstract
Cooling of high temperature systems such as gas turbine blades is one of the most important systems in industrial. In this paper, three dimensional cooling performance on a flat plate is calculated by a 3D finite-volume method and the realizable k-ε turbulence model which is the improved of the standard k-ε turbulence model and it can generate data more appropriate for fluid injections and jets. In this investigation, 4 different cases have compared together to find the best cooling case with maximum effectiveness. These cooling cases are including 2 cases of film cooling with console and cylindrical holes, one case of impingement cooling and one case of transpiration (with porous wall) cooling. For validation, the adiabatic cooling effectiveness for the console has been compared with the experimental data. These comparisons have been shown a good agreement between experimental and numerical data. The adiabatic cooling effectiveness, the effects of density ratio (by air and CO2 as a coolant) (DR) and blowing ratio (M) are studied in all cases. The adiabatic cooling effectiveness for console and transpiration cooling cases have compared together for studying the penetration of coolant fluid in the main stream (hot fluid) and showing the temperature and effectiveness distribution . The main purpose of this paper is finding the best cooling techniques with maximum effectiveness and the results have been shown which the designed transpiration cooling model has the best effectiveness respect to other cooling techniques.
N. Sahraiyan, S.m.h. Mohammadi, E. Jahanshahi Javaran,
Volume 20, Issue 2 (1-2020)
Abstract
The application of solar energy for space cooling has been increasingly considered in Iran and other countries in the last two decades. In this study, two different configurations of a solar assisted refrigeration system have been studied. The first system is the combination of a lithium bromide vapor absorption refrigeration system and flat plate collectors. The other system is consisted of a compression refrigeration system and thermal photovoltaic panels. For this purpose, 32% of the roof area of the building has been covered with 105 flat plate collectors, each with a total area of 1.591 m2, or 288 photovoltaic panels each with an area of 0.556 m2. Both systems have been compared in terms of energy, exergy, and economic viewpoints. This comparison has been conducted for providing the 70 kW cooling capacity system required for an office building with an area of 500 m2. The results of this study showed that at an evaporator temperature of 5°C and the ambient temperature of 27°C, the coefficient of performance of the compression chiller is 3.5 and the absorption chiller is 0.71. Also, the total energy efficiency and the total exergy efficiency in the compression chiller system combined with thermal photovoltaic panels are 7.43% and 8.25% respectively. Those two parameters for the absorption chiller combined with flat plate collectors are 9.16% and 6.66%, respectively. In the economic analysis, the annual life cycle cost for the compression chiller system combined with thermal photovoltaic collectors is 9710 $ and this cost for the absorption chiller system combined with flat plate collectors is estimated 7649 $.
Mohammad Saadatbakhsh, Sadegh Sadeghzadeh,
Volume 24, Issue 5 (4-2024)
Abstract
Superhydrophobic surfaces have gained significant attention as a promising approach for drag reduction of submerged objects. Accurate evaluation and prediction of drag reduction induced by these surfaces require expensive experimental measurements, numerical simulations, or the development of reliable models and correlations. In this paper, a model is proposed for calculating the skin friction coefficient and drag reduction of superhydrophobic flat surfaces. Utilizing previous data on the skin friction coefficient of flat surfaces under no-slip boundary conditions, a model is developed to estimate the skin friction reduction and skin friction coefficient of these surfaces after applying superhydrophobic coatings. The validity of the model is verified by comparing its results with those of computational fluid dynamics (CFD) simulations of flow over a flat plate at different velocities. The results of the model and simulations indicate that for inlet velocities of 1, 5, and 25 m/s and a slip length of 50 μm, drag reductions of 15%, 41%, and 77%, respectively, are expected. Additionally, the skin friction reduction increases with increasing flow Reynolds number. The developed model is validated for flat surfaces and its ability to accurately estimate the skin friction coefficient and drag force of these surfaces is thoroughly examined. However, further investigations are required to assess the model's validity for curved surfaces and variable slip lengths.
