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Papers by jaber almutairi

Energies, Dec 14, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

ERCOFTAC series, 2015

Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings ... more Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings at a low Reynolds number.

Springer eBooks, 2010

Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at low Reynol... more Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at low Reynolds number. The method is validated against direct numerical simulation for an airfoil test case with a transitional separation bubble. The role of the sub grid model is considered together with explicit filtering and it is found that results are improved when both methods are used in combination. Large fluctuations in lift coefficient are observed during the initial stages of calculations near stall and it is found that these are sensitive to the spanwise extent of the computational domain.

42nd AIAA Fluid Dynamics Conference and Exhibit, Jun 25, 2012

ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon usin... more ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon using large-eddy simulation. Four simulations were carried out for flow around a NACA 0012 airfoil with Reynolds number of 50,000 and Mach number M-infinity = 0.4 at angles of attack of 9.25, 9.29, 9.4, and 9.6 deg. The results clearly indicate that natural low-frequency flow oscillation is taking place. The oscillations are self-sustained and caused by periodic bubble forming and bubble bursting on the suction side. The low-frequency oscillation phenomenon was found to exist over a range of angles of attack near stall. Computed maximum reverse flow inside the bubble indicates an absolute instability mechanism. The time- and span-averaged flowfleld as well as the instantaneous turbulent flowfield illustrated the dynamics of low-frequency oscillation near stall. The location of transition is shown to move downstream during bubble bursting. Spectral analysis of the surrounding acoustic field reveals that the observed phenomenon affects the circulation around the entire airfoil. Analysis of the flowfield led to the proposition of a mechanism for low-frequency flow oscillations near stall in which the separated shear layers from the leading edge and the trailing edge play a major role in driving the separated flow to reattachment.

Bulletin of the American Physical Society, Nov 26, 2013

ERCOFTAC series, Oct 8, 2017

Flow control plays an important role in enhancing aerodynamic characteristics of airfoils such as... more Flow control plays an important role in enhancing aerodynamic characteristics of airfoils such as reducing skin-friction drag, advancing or delaying transition, preventing or triggering separation, and enhancing the lift coefficient. In the review paper of Gad-el-Hak and Bushnell (J Fluid Eng 113, 5–30 (1991)) [6], they provided an extensive review of flow control techniques such as blowing (J Aircr 25, 817–821 (1989)) [11], suction (AIAA J 25, 759–760 (1987)) [13] acoustic excitation (J Fluid Mech 182, 127–148 (1987)) [18], periodic forcing excitation by imposing an oscillating wire or flap upstream the separation location (AIAA J 24, 1956–1963 (1986)) [15], (Phys Fluids Fluid Dyn 2, 179–181 (1989)) [10], (AIAA J 27(6), 820–821 (1989)) [5] and utilization of magnetic field through plasma actuators as documented by Post and Corke (AIAA J 42(11), 2177–2184 (2004)) [12] and Huang et al. (AIAA J 44(7), 1477–1487 (2006)) [7].

Energies

This paper proposes correlation equations of heat transfer and pressure drop for the design and o... more This paper proposes correlation equations of heat transfer and pressure drop for the design and operation of tunnel kilns loaded with lattice brick settings of different geometrical parameters in the form of Nusselt number and friction factor. The developed correlation equations considered parameters that were not investigated in previous studies, such as the relative roughness of the bricks and the stack channels, and they also extended the Reynolds numbers to a practical range that was not covered before in a simple, practical form. The correlation equations are valid for Reynolds number between 125 and 10,200, Prandtl number between 0.68 and 0.73, brick’s relative roughness between 0.23 and 0.93, voidage fraction between 0.48 and 0.653, and the geometrical parameters of the tested lattice brick settings. The achieved correlations of the Nusselt number and the friction factor are well compared with the available correlations in the literature in their valid range of parameters. It...

Energies

This paper investigates the combined effect of the kiln or brick surface roughness and the brick ... more This paper investigates the combined effect of the kiln or brick surface roughness and the brick lattice setting density on the fluid flow and heat transfer characteristics in tunnel kilns. The flow uniformity, pressure drop, convective heat transfer coefficient (CHTC), and pumping power are studied. A high-density setting (HDS), which comprises 768 bricks, and a low-density setting (LDS), which comprises 512 bricks, are tested for kiln boundaries and brick surface roughness levels of 0, 1, 2, 3, and 4 mm. The investigation is conducted using a 3D-CFD model with the k-ω turbulence model. The surface roughness changes from 0 to 4 mm for either kiln walls or bricks while fixing the other. The results show that increasing the tunnel kiln surface roughness from 0 to 4 mm increases the pressure drop of both the HDS and LDS by about 13.5%. It also increases the established CHTC value of the LDS more than the HDS by about 23% for all tested roughness levels. Changing the brick surface roug...

World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering, 2017

Authors : Jaber H. Almutairi, Hosny Z. Abou-Ziyan, Issa F. Almesri, Mosab A. Alrahmani Abstract :... more Authors : Jaber H. Almutairi, Hosny Z. Abou-Ziyan, Issa F. Almesri, Mosab A. Alrahmani Abstract : The present work investigates the behavior of fluid flow inside tunnel kilns using 3D-CFD (Computational Fluid Dynamics) simulations. The CFD simulations are carried out with the FLUENT software and validated against experimental results on fluid flow and heat transfer in tunnel kilns. A grid dependency study is conducted in the current work to improve the accuracy of the results. Three turbulence models k–ω, standard k–ε, and RNG k–ε are tested where k–ω model gives the best results in comparison with the experiment. The numerical results reveal an intriguing phenomenon where a long flow separation zone behind the setting is observed under different geometric and operation conditions. It was found that the uniformity of flow distribution can be substantially improved by rearranging the geometrical parameters of brick setting relative to kiln/setting. This improvement of flow distributi...

Direct and Large-Eddy Simulation IX, 2015

Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings ... more Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings at a low Reynolds number.

Journal of Thermal Science and Engineering Applications, 2021

This paper presents the effect of brick and kiln wall roughness on the fluid flow, pressure drop,... more This paper presents the effect of brick and kiln wall roughness on the fluid flow, pressure drop, and convection and radiation heat transfer in tunnel kilns. The surface roughness of 0–4 mm is investigated for bricks and tunnel boundary. Another wall roughness of 10 mm is considered to explore the effect of significant defects in the tunnel boundary. The study is conducted using a three-dimensional computational fluid dynamics (CFD) model based on the finite volume method with the k – ω turbulence model. The convective heat transfer coefficients enhance by 45% and 97%, and the pressure drop increases by 25.1% and 80.4% as the brick roughness is increased from 0 to 1 mm and 0 to 4 mm, respectively. The ratio of heat transfer rate to pumping power reaches its maximum at a brick roughness of 2 mm. These results provide essential knowledge about the acceptable range of brick roughness for manufacturers. As the tunnel boundary roughness is increased from 0 to 1 and 0 to 10 mm, the heat t...

Journal of Thermal Science and Engineering Applications

This paper reports the effect of setting density on flow uniformity, pressure drop, pumping power... more This paper reports the effect of setting density on flow uniformity, pressure drop, pumping power, and convective heat transfer coefficients (CHTCs). High-density setting (HDS) comprises 768 bricks, and low-density setting (LDS) contains 512 bricks are tested for different inlet air velocities using both local and average approaches. The investigation is carried out using a 3D-computational fluid dynamics (CFD) model with k–ω turbulence model. Both settings are validated against experimental data reported in the literature with errors less than 1.9% for pressure drop and −1.0% for brick surface temperature. The reported results indicated that the LDS has distinct benefits over the HDS as it enhances the flow uniformity, particularly in the stack channels. Also, LDS attains lower pressure drop, pumping power, and firing time than HDS by 45.93%, 50%, and 35%, respectively. In addition, LDS produces larger CHTCs, rates of heat transfer for individual bricks, and the ratio of heat trans...

Theoretical and Computational Fluid Dynamics

International Journal of Mechanical Sciences

Journal of Thermal Science and Engineering Applications

This paper reports the local multifaceted and area-averaged convective heat transfer coefficients... more This paper reports the local multifaceted and area-averaged convective heat transfer coefficients (CHTCs) of longitudinal and transverse bricks arranged in lattice brick setting in tunnel kilns, using a three-dimensional (3D) computational fluid dynamics (CFD) model. A mesh sensitivity analysis was performed and the model was validated against reported experimental data in tunnel kilns. Three turbulence models were tested: the standard k–ε, re-normalization group (RNG) k–ε, and k–ω. The k–ω model provided the closest results to the experimental data. The CHTCs from the front, back, left, and right faces of the longitudinal and transverse bricks were calculated under various conditions. Area-averaged CHTCs for bricks were determined from the multifaceted CHTCs. Effects of rows, layers, and walls on faces and area-averaged CHTCs were investigated. A sensitivity analysis was performed to explore the effect of flow channels on the CHTCs. The numerical results showed that the CHTCs are e...

Aerospace Science and Technology

AIAA Journal, 2010

RefDoc Bienvenue - Welcome. Refdoc est un service / is powered by. ...

AIAA Journal, 2002

ABSTRACT Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at l... more ABSTRACT Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at low Reynolds number. The method is validated against direct numerical simulation for an airfoil test case with a transitional separation bubble. The role of the sub grid model is considered together with explicit filtering and it is found that results are improved when both methods are used in combination. Large fluctuations in lift coefficient are observed during the initial stages of calculations near stall and it is found that these are sensitive to the spanwise extent of the computational domain.

AIAA Journal, 2013

ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon usin... more ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon using large-eddy simulation. Four simulations were carried out for flow around a NACA 0012 airfoil with Reynolds number of 50,000 and Mach number M-infinity = 0.4 at angles of attack of 9.25, 9.29, 9.4, and 9.6 deg. The results clearly indicate that natural low-frequency flow oscillation is taking place. The oscillations are self-sustained and caused by periodic bubble forming and bubble bursting on the suction side. The low-frequency oscillation phenomenon was found to exist over a range of angles of attack near stall. Computed maximum reverse flow inside the bubble indicates an absolute instability mechanism. The time- and span-averaged flowfleld as well as the instantaneous turbulent flowfield illustrated the dynamics of low-frequency oscillation near stall. The location of transition is shown to move downstream during bubble bursting. Spectral analysis of the surrounding acoustic field reveals that the observed phenomenon affects the circulation around the entire airfoil. Analysis of the flowfield led to the proposition of a mechanism for low-frequency flow oscillations near stall in which the separated shear layers from the leading edge and the trailing edge play a major role in driving the separated flow to reattachment.

Energies, Dec 14, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

ERCOFTAC series, 2015

Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings ... more Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings at a low Reynolds number.

Springer eBooks, 2010

Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at low Reynol... more Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at low Reynolds number. The method is validated against direct numerical simulation for an airfoil test case with a transitional separation bubble. The role of the sub grid model is considered together with explicit filtering and it is found that results are improved when both methods are used in combination. Large fluctuations in lift coefficient are observed during the initial stages of calculations near stall and it is found that these are sensitive to the spanwise extent of the computational domain.

42nd AIAA Fluid Dynamics Conference and Exhibit, Jun 25, 2012

ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon usin... more ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon using large-eddy simulation. Four simulations were carried out for flow around a NACA 0012 airfoil with Reynolds number of 50,000 and Mach number M-infinity = 0.4 at angles of attack of 9.25, 9.29, 9.4, and 9.6 deg. The results clearly indicate that natural low-frequency flow oscillation is taking place. The oscillations are self-sustained and caused by periodic bubble forming and bubble bursting on the suction side. The low-frequency oscillation phenomenon was found to exist over a range of angles of attack near stall. Computed maximum reverse flow inside the bubble indicates an absolute instability mechanism. The time- and span-averaged flowfleld as well as the instantaneous turbulent flowfield illustrated the dynamics of low-frequency oscillation near stall. The location of transition is shown to move downstream during bubble bursting. Spectral analysis of the surrounding acoustic field reveals that the observed phenomenon affects the circulation around the entire airfoil. Analysis of the flowfield led to the proposition of a mechanism for low-frequency flow oscillations near stall in which the separated shear layers from the leading edge and the trailing edge play a major role in driving the separated flow to reattachment.

Bulletin of the American Physical Society, Nov 26, 2013

ERCOFTAC series, Oct 8, 2017

Flow control plays an important role in enhancing aerodynamic characteristics of airfoils such as... more Flow control plays an important role in enhancing aerodynamic characteristics of airfoils such as reducing skin-friction drag, advancing or delaying transition, preventing or triggering separation, and enhancing the lift coefficient. In the review paper of Gad-el-Hak and Bushnell (J Fluid Eng 113, 5–30 (1991)) [6], they provided an extensive review of flow control techniques such as blowing (J Aircr 25, 817–821 (1989)) [11], suction (AIAA J 25, 759–760 (1987)) [13] acoustic excitation (J Fluid Mech 182, 127–148 (1987)) [18], periodic forcing excitation by imposing an oscillating wire or flap upstream the separation location (AIAA J 24, 1956–1963 (1986)) [15], (Phys Fluids Fluid Dyn 2, 179–181 (1989)) [10], (AIAA J 27(6), 820–821 (1989)) [5] and utilization of magnetic field through plasma actuators as documented by Post and Corke (AIAA J 42(11), 2177–2184 (2004)) [12] and Huang et al. (AIAA J 44(7), 1477–1487 (2006)) [7].

Energies

This paper proposes correlation equations of heat transfer and pressure drop for the design and o... more This paper proposes correlation equations of heat transfer and pressure drop for the design and operation of tunnel kilns loaded with lattice brick settings of different geometrical parameters in the form of Nusselt number and friction factor. The developed correlation equations considered parameters that were not investigated in previous studies, such as the relative roughness of the bricks and the stack channels, and they also extended the Reynolds numbers to a practical range that was not covered before in a simple, practical form. The correlation equations are valid for Reynolds number between 125 and 10,200, Prandtl number between 0.68 and 0.73, brick’s relative roughness between 0.23 and 0.93, voidage fraction between 0.48 and 0.653, and the geometrical parameters of the tested lattice brick settings. The achieved correlations of the Nusselt number and the friction factor are well compared with the available correlations in the literature in their valid range of parameters. It...

Energies

This paper investigates the combined effect of the kiln or brick surface roughness and the brick ... more This paper investigates the combined effect of the kiln or brick surface roughness and the brick lattice setting density on the fluid flow and heat transfer characteristics in tunnel kilns. The flow uniformity, pressure drop, convective heat transfer coefficient (CHTC), and pumping power are studied. A high-density setting (HDS), which comprises 768 bricks, and a low-density setting (LDS), which comprises 512 bricks, are tested for kiln boundaries and brick surface roughness levels of 0, 1, 2, 3, and 4 mm. The investigation is conducted using a 3D-CFD model with the k-ω turbulence model. The surface roughness changes from 0 to 4 mm for either kiln walls or bricks while fixing the other. The results show that increasing the tunnel kiln surface roughness from 0 to 4 mm increases the pressure drop of both the HDS and LDS by about 13.5%. It also increases the established CHTC value of the LDS more than the HDS by about 23% for all tested roughness levels. Changing the brick surface roug...

World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering, 2017

Authors : Jaber H. Almutairi, Hosny Z. Abou-Ziyan, Issa F. Almesri, Mosab A. Alrahmani Abstract :... more Authors : Jaber H. Almutairi, Hosny Z. Abou-Ziyan, Issa F. Almesri, Mosab A. Alrahmani Abstract : The present work investigates the behavior of fluid flow inside tunnel kilns using 3D-CFD (Computational Fluid Dynamics) simulations. The CFD simulations are carried out with the FLUENT software and validated against experimental results on fluid flow and heat transfer in tunnel kilns. A grid dependency study is conducted in the current work to improve the accuracy of the results. Three turbulence models k–ω, standard k–ε, and RNG k–ε are tested where k–ω model gives the best results in comparison with the experiment. The numerical results reveal an intriguing phenomenon where a long flow separation zone behind the setting is observed under different geometric and operation conditions. It was found that the uniformity of flow distribution can be substantially improved by rearranging the geometrical parameters of brick setting relative to kiln/setting. This improvement of flow distributi...

Direct and Large-Eddy Simulation IX, 2015

Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings ... more Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings at a low Reynolds number.

Journal of Thermal Science and Engineering Applications, 2021

This paper presents the effect of brick and kiln wall roughness on the fluid flow, pressure drop,... more This paper presents the effect of brick and kiln wall roughness on the fluid flow, pressure drop, and convection and radiation heat transfer in tunnel kilns. The surface roughness of 0–4 mm is investigated for bricks and tunnel boundary. Another wall roughness of 10 mm is considered to explore the effect of significant defects in the tunnel boundary. The study is conducted using a three-dimensional computational fluid dynamics (CFD) model based on the finite volume method with the k – ω turbulence model. The convective heat transfer coefficients enhance by 45% and 97%, and the pressure drop increases by 25.1% and 80.4% as the brick roughness is increased from 0 to 1 mm and 0 to 4 mm, respectively. The ratio of heat transfer rate to pumping power reaches its maximum at a brick roughness of 2 mm. These results provide essential knowledge about the acceptable range of brick roughness for manufacturers. As the tunnel boundary roughness is increased from 0 to 1 and 0 to 10 mm, the heat t...

Journal of Thermal Science and Engineering Applications

This paper reports the effect of setting density on flow uniformity, pressure drop, pumping power... more This paper reports the effect of setting density on flow uniformity, pressure drop, pumping power, and convective heat transfer coefficients (CHTCs). High-density setting (HDS) comprises 768 bricks, and low-density setting (LDS) contains 512 bricks are tested for different inlet air velocities using both local and average approaches. The investigation is carried out using a 3D-computational fluid dynamics (CFD) model with k–ω turbulence model. Both settings are validated against experimental data reported in the literature with errors less than 1.9% for pressure drop and −1.0% for brick surface temperature. The reported results indicated that the LDS has distinct benefits over the HDS as it enhances the flow uniformity, particularly in the stack channels. Also, LDS attains lower pressure drop, pumping power, and firing time than HDS by 45.93%, 50%, and 35%, respectively. In addition, LDS produces larger CHTCs, rates of heat transfer for individual bricks, and the ratio of heat trans...

Theoretical and Computational Fluid Dynamics

International Journal of Mechanical Sciences

Journal of Thermal Science and Engineering Applications

This paper reports the local multifaceted and area-averaged convective heat transfer coefficients... more This paper reports the local multifaceted and area-averaged convective heat transfer coefficients (CHTCs) of longitudinal and transverse bricks arranged in lattice brick setting in tunnel kilns, using a three-dimensional (3D) computational fluid dynamics (CFD) model. A mesh sensitivity analysis was performed and the model was validated against reported experimental data in tunnel kilns. Three turbulence models were tested: the standard k–ε, re-normalization group (RNG) k–ε, and k–ω. The k–ω model provided the closest results to the experimental data. The CHTCs from the front, back, left, and right faces of the longitudinal and transverse bricks were calculated under various conditions. Area-averaged CHTCs for bricks were determined from the multifaceted CHTCs. Effects of rows, layers, and walls on faces and area-averaged CHTCs were investigated. A sensitivity analysis was performed to explore the effect of flow channels on the CHTCs. The numerical results showed that the CHTCs are e...

Aerospace Science and Technology

AIAA Journal, 2010

RefDoc Bienvenue - Welcome. Refdoc est un service / is powered by. ...

AIAA Journal, 2002

ABSTRACT Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at l... more ABSTRACT Large-eddy simulation is used to study the stalling behaviour of a NACA0012 airfoil at low Reynolds number. The method is validated against direct numerical simulation for an airfoil test case with a transitional separation bubble. The role of the sub grid model is considered together with explicit filtering and it is found that results are improved when both methods are used in combination. Large fluctuations in lift coefficient are observed during the initial stages of calculations near stall and it is found that these are sensitive to the spanwise extent of the computational domain.

AIAA Journal, 2013

ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon usin... more ABSTRACT The present work investigates the natural low-frequency flow oscillation phenomenon using large-eddy simulation. Four simulations were carried out for flow around a NACA 0012 airfoil with Reynolds number of 50,000 and Mach number M-infinity = 0.4 at angles of attack of 9.25, 9.29, 9.4, and 9.6 deg. The results clearly indicate that natural low-frequency flow oscillation is taking place. The oscillations are self-sustained and caused by periodic bubble forming and bubble bursting on the suction side. The low-frequency oscillation phenomenon was found to exist over a range of angles of attack near stall. Computed maximum reverse flow inside the bubble indicates an absolute instability mechanism. The time- and span-averaged flowfleld as well as the instantaneous turbulent flowfield illustrated the dynamics of low-frequency oscillation near stall. The location of transition is shown to move downstream during bubble bursting. Spectral analysis of the surrounding acoustic field reveals that the observed phenomenon affects the circulation around the entire airfoil. Analysis of the flowfield led to the proposition of a mechanism for low-frequency flow oscillations near stall in which the separated shear layers from the leading edge and the trailing edge play a major role in driving the separated flow to reattachment.