ABSTRACT The aim of this work is to optimize the geometric shape in enclosures similar to the squ... more ABSTRACT The aim of this work is to optimize the geometric shape in enclosures similar to the square cavity in natural convection regime. The desired configuration differs from the classical cavity by the geometrical form of the hot wall to be defined. The procedure is based on a sequential quadratic programming in which the wall is parameterized by Bezier curves. The numerical optimization method developed is the outcome of combining a flow calculation method and a constrained minimization method. Investigations have been performed for different inclination angles and various Rayleigh numbers. The numerical results show that optimization is relevant since the heat transfer rate decreases considerably by comparison with the square and the undulated cavities. It is also found that the beneficial optimization occurs for high Rayleigh numbers.
ABSTRACT In the present study, a numerical simulation is carried out in order to optimize the len... more ABSTRACT In the present study, a numerical simulation is carried out in order to optimize the length of the mixing part of a T-junction to obtain a homogenous temperature distribution at the outlet. Different RANS turbulence models are tested: the Realizable k-ε the k-ω standard and the k-ω SST. The behavior of turbulent mixing flow in the mixing part of the pipe has helped in understanding the causes of discrepancy between the models used. The test case analysed in this paper is an unsteady state three-dimensional turbulent flow. The numerical results obtained show that there is a difference in the prediction of the thermal field when different models are used. The results obtained for both k-ω standard and SST models are closer compared with those given by the Realizable k-ε model. The numerical results show that a distance of x/L = 0.625 from the branch is enough to supply devices with a constant temperature.
Steady three-dimensional and two free surface waves generated by moving bodies are presented, the... more Steady three-dimensional and two free surface waves generated by moving bodies are presented, the flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. The results of several simulations are reported. The first study was performed for NACA0012 of hydrofoil with different meshes, this section is analyzed at h/c= 1, 0345 for 2D. In the second simulation a mathematically defined Wigley hull form is used to investigate the application of a commercial CFD code in prediction of the total resistance and its components from tangential and normal forces on the hull wetted surface. The computed resistance and wave profiles are used to estimate the coefficient of the total resistance for Wigley hull advancing in calm water under steady conditions. The commercial CFD software FLUENT version 12 is used for the com...
Journal of Naval Architecture and Marine Engineering, 2020
New contra-rotating four-bladed DTMB propeller configurations operating in open water are numeric... more New contra-rotating four-bladed DTMB propeller configurations operating in open water are numerically studied to determine their hydrodynamic performances. The unsteady turbulent flow around propellers is modelled by RANS equations with Kω SST model then solved by a CFD code. The computational domain is divided in two blocks linked with a rotating interface. The obtained results show that thrust and efficiency of the contra-rotating (CRP) increase compared to the single propeller, leading to a significant reduction of the propeller diameter. The variation in axial spacing and angular displacement seems to have little effect on the CRP efficiency. The results also show that the thrust can be further improved by adopting a moderate negative twist angle of the rear propeller. Keywords: CRP contra-rotating propeller, axial spacing, angular spacing, twist angle, CFD.
This paper deals with numerical simulation of stationary flow around a marine propeller. The aim ... more This paper deals with numerical simulation of stationary flow around a marine propeller. The aim is to reproduce the hydrodynamic turbulent flow around the Wageningen B serie propellers in open water using the ANSYS FLUENT code and the RANS approach. The computational domain consists of an inter-blade channel with periodic boundaries, meshed with tetrahedral cells. The turbulence is modeled with the k-ω. The obtained results provide good agreement with the available experimental data and show that the blades number affects considerably the marine propellers performances. It is interesting to notice that the six blades propeller is the best adapted one for the open water flows.
The turbulent and thermal mixing in a vertically oriented T-junction is investigated numerically ... more The turbulent and thermal mixing in a vertically oriented T-junction is investigated numerically using ANSYS FLUENT software. By taking account the buoyancy forces, a steady state three-dimensional turbulent flow is considered with a Reynolds number of 0.4×105 at the cold inlet and 3.3×105 at the hot entrance. The k-ε standard model with standard wall function is chosen to provide closure for the Reynolds stress tensor. The numerical results presented in the form of velocity vectors field and contours of temperature distribution gave a good prediction of the dynamic and the thermal fields namely in the mixing region where a reversed flow is captured.
Steady three-dimensional and two free surface waves generated by moving bodies are presented, the... more Steady three-dimensional and two free surface waves generated by moving bodies are presented, the flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. The results of several simulations are reported. The first study was performed for NACA0012 of hydrofoil with different meshes, this section is analyzed at h/c= 1, 0345 for 2D. In the second simulation a mathematically defined Wigley hull form is used to investigate the application of a commercial CFD code in prediction of the total resistance and its components from tangential and normal forces on the hull wetted surface. The computed resistance and wave profiles are used to estimate the coefficient of the total resistance for Wigley hull advancing in calm water under steady conditions. The commercial CFD software FLUENT version 12 is used for the com...
ABSTRACT The aim of this work is to optimize the geometric shape in enclosures similar to the squ... more ABSTRACT The aim of this work is to optimize the geometric shape in enclosures similar to the square cavity in natural convection regime. The desired configuration differs from the classical cavity by the geometrical form of the hot wall to be defined. The procedure is based on a sequential quadratic programming in which the wall is parameterized by Bezier curves. The numerical optimization method developed is the outcome of combining a flow calculation method and a constrained minimization method. Investigations have been performed for different inclination angles and various Rayleigh numbers. The numerical results show that optimization is relevant since the heat transfer rate decreases considerably by comparison with the square and the undulated cavities. It is also found that the beneficial optimization occurs for high Rayleigh numbers.
ABSTRACT In the present study, a numerical simulation is carried out in order to optimize the len... more ABSTRACT In the present study, a numerical simulation is carried out in order to optimize the length of the mixing part of a T-junction to obtain a homogenous temperature distribution at the outlet. Different RANS turbulence models are tested: the Realizable k-ε the k-ω standard and the k-ω SST. The behavior of turbulent mixing flow in the mixing part of the pipe has helped in understanding the causes of discrepancy between the models used. The test case analysed in this paper is an unsteady state three-dimensional turbulent flow. The numerical results obtained show that there is a difference in the prediction of the thermal field when different models are used. The results obtained for both k-ω standard and SST models are closer compared with those given by the Realizable k-ε model. The numerical results show that a distance of x/L = 0.625 from the branch is enough to supply devices with a constant temperature.
Steady three-dimensional and two free surface waves generated by moving bodies are presented, the... more Steady three-dimensional and two free surface waves generated by moving bodies are presented, the flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. The results of several simulations are reported. The first study was performed for NACA0012 of hydrofoil with different meshes, this section is analyzed at h/c= 1, 0345 for 2D. In the second simulation a mathematically defined Wigley hull form is used to investigate the application of a commercial CFD code in prediction of the total resistance and its components from tangential and normal forces on the hull wetted surface. The computed resistance and wave profiles are used to estimate the coefficient of the total resistance for Wigley hull advancing in calm water under steady conditions. The commercial CFD software FLUENT version 12 is used for the com...
Journal of Naval Architecture and Marine Engineering, 2020
New contra-rotating four-bladed DTMB propeller configurations operating in open water are numeric... more New contra-rotating four-bladed DTMB propeller configurations operating in open water are numerically studied to determine their hydrodynamic performances. The unsteady turbulent flow around propellers is modelled by RANS equations with Kω SST model then solved by a CFD code. The computational domain is divided in two blocks linked with a rotating interface. The obtained results show that thrust and efficiency of the contra-rotating (CRP) increase compared to the single propeller, leading to a significant reduction of the propeller diameter. The variation in axial spacing and angular displacement seems to have little effect on the CRP efficiency. The results also show that the thrust can be further improved by adopting a moderate negative twist angle of the rear propeller. Keywords: CRP contra-rotating propeller, axial spacing, angular spacing, twist angle, CFD.
This paper deals with numerical simulation of stationary flow around a marine propeller. The aim ... more This paper deals with numerical simulation of stationary flow around a marine propeller. The aim is to reproduce the hydrodynamic turbulent flow around the Wageningen B serie propellers in open water using the ANSYS FLUENT code and the RANS approach. The computational domain consists of an inter-blade channel with periodic boundaries, meshed with tetrahedral cells. The turbulence is modeled with the k-ω. The obtained results provide good agreement with the available experimental data and show that the blades number affects considerably the marine propellers performances. It is interesting to notice that the six blades propeller is the best adapted one for the open water flows.
The turbulent and thermal mixing in a vertically oriented T-junction is investigated numerically ... more The turbulent and thermal mixing in a vertically oriented T-junction is investigated numerically using ANSYS FLUENT software. By taking account the buoyancy forces, a steady state three-dimensional turbulent flow is considered with a Reynolds number of 0.4×105 at the cold inlet and 3.3×105 at the hot entrance. The k-ε standard model with standard wall function is chosen to provide closure for the Reynolds stress tensor. The numerical results presented in the form of velocity vectors field and contours of temperature distribution gave a good prediction of the dynamic and the thermal fields namely in the mixing region where a reversed flow is captured.
Steady three-dimensional and two free surface waves generated by moving bodies are presented, the... more Steady three-dimensional and two free surface waves generated by moving bodies are presented, the flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. The results of several simulations are reported. The first study was performed for NACA0012 of hydrofoil with different meshes, this section is analyzed at h/c= 1, 0345 for 2D. In the second simulation a mathematically defined Wigley hull form is used to investigate the application of a commercial CFD code in prediction of the total resistance and its components from tangential and normal forces on the hull wetted surface. The computed resistance and wave profiles are used to estimate the coefficient of the total resistance for Wigley hull advancing in calm water under steady conditions. The commercial CFD software FLUENT version 12 is used for the com...
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Papers by Mustapha Belkadi