Martin Skote | Nanyang Technological University (original) (raw)
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Papers by Martin Skote
In recent years direct numerical simulation (DNS) of turbulent boundary layers has become an impo... more In recent years direct numerical simulation (DNS) of turbulent boundary layers has become an important complement to experiments for obtaining turbulence data. The rst DNS of turbulent boundary layers in an adverse pressure gradient (APG) were the temporal simulations performed by Spalart & Leonard 13] where they used a similarity coordinate system. Spalart & Watmu 14] compared experiments and DNS of an APG turbulent boundary layer in a varying pressure gradient and they found good agreement. Skote et al.
Direct numerical simulation(DNS) of fundamental fluid flow simulation using 3-dimensional Navier-... more Direct numerical simulation(DNS) of fundamental fluid flow simulation using 3-dimensional Navier-Stokes equations is a typical large scale computing which requires high performance computer with vector and parallel processing. In the present paper a turbulent boundary layer flow simulation with strong adverse pressure gradient on a flat plate was made on NAL Numerical Wind Tunnel. Boundary layer subjected to a strong adverse pressure gradient creates a separation bubble followed by a region with small, but positive, skin friction. This flow case contains features that has proven to be difficult to predict with existing turbulence models. The data from present simulation are used for investigation of the scalings near the wall, a crucial concept with respect to turbulence models. The present analysis uses spectral methods and the parallelization was done using MPI(Message-Passing Interface). A good efficiency was obtained in NWT. To compare with other machine performances, previous computations on T3E and SP2 are also shown.
European Biophysics Journal With Biophysics Letters, Jan 1, 2006
A novel polymerase chain reaction (PCR) method is presented that utilizes Coriolis and centrifuga... more A novel polymerase chain reaction (PCR) method is presented that utilizes Coriolis and centrifugal effects, produced by rotation of the sample disc, in order to increase internal circulatory rates, and with them temperature homogenization and mixing speeds. A proof of concept has been presented by testing a rapid 45-cycle PCR DNA amplification protocol. During the repeated heating and cooling that constitutes a PCR process, the 100 μL samples were rotated at a speed equivalent to an effective acceleration of gravity of 7,000 g. A cycle time of 20.5 s gave a total process time of 15 min to complete the 45 cycles. A theoretical and numerical analysis of the resulting flow, which describes the increased mixing and temperature homogenization, is presented. The device gives excellent reaction speed efficiency, which is beneficial for rapid PCR.
Reynolds stress budgets for both Couette and boundary layer flows are evaluated and presented. Da... more Reynolds stress budgets for both Couette and boundary layer flows are evaluated and presented. Data are taken from direct numerical simulations of rotating and non-rotating plane turbulent Couette flow and turbulent boundary layer with and without adverse pressure gradient. Comparison of the total shear stress for the two types of flows suggests that the Couette case may be regarded as the high Reynolds number limit for the boundary layer flow close to the wall. The limit values of turbulence statistics close to the wall for the boundary layer for increasing Reynolds number approach the corresponding Couette flow values. The direction of rotation is chosen so that it has a stabilizing effect, whereas the adverse pressure gradient is destabilizing. The pressure-strain rate tensor in the Couette flow case is presented for a split into slow, rapid and Stokes terms. Most of the influence from rotation is located to the region close to the wall, and both the slow and rapid parts are affected. The anisotropy for the boundary layer decreases for higher Reynolds number, reflecting the larger separation of scales, and becomes close to that for Couette flow. The adverse pressure gradient has a strong weakening effect on the anisotropy. All of the data presented here are available on the web [36].
Eleventh Symposium on Turbulent Shear Flows : Grenoble, France, September 8-10, 1997, 33:13 - 33:18
Atmospheric Environment, Jan 1, 2005
The purpose of the paper is to examine the relation between urban morphology (three-dimensional s... more The purpose of the paper is to examine the relation between urban morphology (three-dimensional structure) and windiness. We regard a city as a porous obstacle, which is open at the top. We consider the interaction between the atmospheric boundary layer and a city to be both a function of the overall shape (silhouette or skyline) and the internal resistance to the flow caused by the friction when the wind flows over the urban surfaces. We regard the street pattern as an interconnected flow network with the crossings as nodes. Flow along the streets is generated by pressure differences.We here use a highly idealized city model consisting of a circular block divided into two or four equally large sectors. Two types of cases are studied, the first with only one street through the city model with different angles between the street and the oncoming wind. The second case also contains a perpendicularly crossing street (through the center). Both wind tunnel experiments and numerical flow computations (computational fluid dynamics, CFD) are used and compared. The general agreement between the two is good and the CFD method offers new possibilities for quantifying the urban wind environment.
Journal of Fluid Mechanics, Jan 1, 2002
In recent years direct numerical simulation (DNS) of turbulent boundary layers has become an impo... more In recent years direct numerical simulation (DNS) of turbulent boundary layers has become an important complement to experiments for obtaining turbulence data. The rst DNS of turbulent boundary layers in an adverse pressure gradient (APG) were the temporal simulations performed by Spalart & Leonard 13] where they used a similarity coordinate system. Spalart & Watmu 14] compared experiments and DNS of an APG turbulent boundary layer in a varying pressure gradient and they found good agreement. Skote et al.
Direct numerical simulation(DNS) of fundamental fluid flow simulation using 3-dimensional Navier-... more Direct numerical simulation(DNS) of fundamental fluid flow simulation using 3-dimensional Navier-Stokes equations is a typical large scale computing which requires high performance computer with vector and parallel processing. In the present paper a turbulent boundary layer flow simulation with strong adverse pressure gradient on a flat plate was made on NAL Numerical Wind Tunnel. Boundary layer subjected to a strong adverse pressure gradient creates a separation bubble followed by a region with small, but positive, skin friction. This flow case contains features that has proven to be difficult to predict with existing turbulence models. The data from present simulation are used for investigation of the scalings near the wall, a crucial concept with respect to turbulence models. The present analysis uses spectral methods and the parallelization was done using MPI(Message-Passing Interface). A good efficiency was obtained in NWT. To compare with other machine performances, previous computations on T3E and SP2 are also shown.
European Biophysics Journal With Biophysics Letters, Jan 1, 2006
A novel polymerase chain reaction (PCR) method is presented that utilizes Coriolis and centrifuga... more A novel polymerase chain reaction (PCR) method is presented that utilizes Coriolis and centrifugal effects, produced by rotation of the sample disc, in order to increase internal circulatory rates, and with them temperature homogenization and mixing speeds. A proof of concept has been presented by testing a rapid 45-cycle PCR DNA amplification protocol. During the repeated heating and cooling that constitutes a PCR process, the 100 μL samples were rotated at a speed equivalent to an effective acceleration of gravity of 7,000 g. A cycle time of 20.5 s gave a total process time of 15 min to complete the 45 cycles. A theoretical and numerical analysis of the resulting flow, which describes the increased mixing and temperature homogenization, is presented. The device gives excellent reaction speed efficiency, which is beneficial for rapid PCR.
Reynolds stress budgets for both Couette and boundary layer flows are evaluated and presented. Da... more Reynolds stress budgets for both Couette and boundary layer flows are evaluated and presented. Data are taken from direct numerical simulations of rotating and non-rotating plane turbulent Couette flow and turbulent boundary layer with and without adverse pressure gradient. Comparison of the total shear stress for the two types of flows suggests that the Couette case may be regarded as the high Reynolds number limit for the boundary layer flow close to the wall. The limit values of turbulence statistics close to the wall for the boundary layer for increasing Reynolds number approach the corresponding Couette flow values. The direction of rotation is chosen so that it has a stabilizing effect, whereas the adverse pressure gradient is destabilizing. The pressure-strain rate tensor in the Couette flow case is presented for a split into slow, rapid and Stokes terms. Most of the influence from rotation is located to the region close to the wall, and both the slow and rapid parts are affected. The anisotropy for the boundary layer decreases for higher Reynolds number, reflecting the larger separation of scales, and becomes close to that for Couette flow. The adverse pressure gradient has a strong weakening effect on the anisotropy. All of the data presented here are available on the web [36].
Eleventh Symposium on Turbulent Shear Flows : Grenoble, France, September 8-10, 1997, 33:13 - 33:18
Atmospheric Environment, Jan 1, 2005
The purpose of the paper is to examine the relation between urban morphology (three-dimensional s... more The purpose of the paper is to examine the relation between urban morphology (three-dimensional structure) and windiness. We regard a city as a porous obstacle, which is open at the top. We consider the interaction between the atmospheric boundary layer and a city to be both a function of the overall shape (silhouette or skyline) and the internal resistance to the flow caused by the friction when the wind flows over the urban surfaces. We regard the street pattern as an interconnected flow network with the crossings as nodes. Flow along the streets is generated by pressure differences.We here use a highly idealized city model consisting of a circular block divided into two or four equally large sectors. Two types of cases are studied, the first with only one street through the city model with different angles between the street and the oncoming wind. The second case also contains a perpendicularly crossing street (through the center). Both wind tunnel experiments and numerical flow computations (computational fluid dynamics, CFD) are used and compared. The general agreement between the two is good and the CFD method offers new possibilities for quantifying the urban wind environment.
Journal of Fluid Mechanics, Jan 1, 2002