Fluctuating lift and drag on a long cylinder of square cross-section in a smooth and in a turbulent stream

1966 ◽  
Vol 25 (3) ◽  
pp. 481-494 ◽  
Author(s):  
B. J. Vickery
Keyword(s):  
Cross Section ◽  
Large Scale ◽  
Circular Cross Section ◽  
Square Cylinder ◽  
Marked Influence ◽  
Fluctuating Pressure ◽  
Scale Turbulence ◽  
Lift And Drag ◽  
Long Cylinder

The paper presents the results of measurements of fluctuating lift and drag on a long square cylinder. The measurements include the correlation of lift along the cylinder and the distribution of fluctuating pressure on a cross-section. The magnitude of the fluctuating lift was found to be considerably greater than that for a circular cross-section and the spanwise correlation much stronger.It was found that the presence of large-scale turbulence in the stream had a marked influence on both the steady and the fluctuating forces. The most significant changes were at small angles of attack (%alpha; < 10°) and included a reduction in base suction and a decrease in fluctuating lift of about 50%.

Geometry Effects in Eulerian/Granular Simulation of a Turbulent FCC Riser with a (kg-?g)-KTGF Model

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Hamid Reza Nazif ◽  
Hassan Basirat Tabrizi ◽  
Farhad A Farhadpour
Keyword(s):  
Cross Section ◽  
Large Scale ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Good Prediction ◽  
Model Predictions ◽  
Secondary Circulations ◽  
Sharp Corners ◽  
Granular Simulation

Three-dimensional, transient turbulent particulate flow in an FCC riser is modeled using an Eulerian/Granular approach. The turbulence in the gas phase is described by a modified realizable (kg-?g) closure model and the kinetic theory of granular flow (KTGF) is employed for the particulate phase. Separate simulations are conducted for a rectangular and a cylindrical riser with similar dimensions. The model predictions are validated against experimental data of Sommerfeld et al (2002) and also compared with the previously reported LES-KTGF simulations of Hansen et al (2003) for the rectangular riser. The (kg-?g)-KTGF model does not perform as well as the LES-KTGF model for the riser with a rectangular cross section. This is because, unlike the more elaborate LES-KTGF model, the simpler (kg-?g)-KTGF model cannot capture the large scale secondary circulations induced by anisotropic turbulence at the corners of the rectangular riser. In the cylindrical geometry, however, the (kg-?g)-KTGF model gives good prediction of the data and is a viable alternative to the more complex LES-KTGF model. This is not surprising as the circulations in the riser with a circular cross section are due to the curvature of the walls and not due to the presence of sharp corners.

The effects of turbulence on the mean flow past square rods

1983 ◽  
Vol 137 ◽  
pp. 331-345 ◽  
Author(s):  
Y. Nakamura ◽  
Y. Ohya
Keyword(s):  
Growth Rate ◽  
Shear Layer ◽  
Cross Section ◽  
Large Scale ◽  
Small Scale ◽  
Mean Flow ◽  
Flow Past ◽  
The Mean ◽  
Scale Turbulence ◽  
Main Effects

There are two main effects of turbulence on the mean flow past rods of square cross-section aligned with the approaching flow. Small-scale turbulence increases the growth rate of the shear layer, while large-scale turbulence enhances the roll-up of the shear layer. The consequences of these depend on the length of a square rod. The mean base pressure of a square rod varies considerably with turbulence intensity and scale as well as with its length.

Simulation of Vortex-Shedding Flow About a Circular Cylinder at High Reynolds Numbers

1990 ◽  
Vol 112 (2) ◽  
pp. 155-161 ◽  
Author(s):  
Charles C. S. Song ◽  
Mingshun Yuan
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Large Scale ◽  
Flow Equations ◽  
Large Scale Vortex ◽  
Scale Turbulence ◽  
High Reynolds ◽  
Lift And Drag ◽  
Secondary Vortices ◽  
Volume Method

Vortex shedding over a circular cylinder is modeled based on the weakly compressible flow equations with a simple subgrid scale turbulence model and a simple hybrid boundary condition. An explicit finite volume method is used. A subcritical and a supercritical case are computed. It is shown that the large-scale vortex-shedding phenomenon, the primary vortices, and the related oscillatory lift and drag can be calculated fairly well with a grid system coarser than the boundary layer thickness. The secondary vortices and the related higher frequency oscillations are also calculated by using somewhat finer grids.

Impact Theory Calculations of the Lift and Drag of Ducted Bodies

1962 ◽  
Vol 13 (4) ◽  
pp. 327-348 ◽  
Author(s):  
J. Tinkler
Keyword(s):  
Skin Friction ◽  
Cross Section ◽  
Circular Cross Section ◽  
External Pressure ◽  
Impact Theory ◽  
Overall Performance ◽  
Mach Numbers ◽  
Lift And Drag ◽  
Drag Ratio

SummaryNewtonian impact theory has been used to estimate the external pressure forces on ducted bodies of rectangular, circular and semi-circular cross section. With an allowance for skin friction (or other incidence-independent drag) it is shown that maximum lift/drag ratios of about three to four are possible with little effect of body geometry provided that short and very divergent, or tall and narrow rectangular ducts are avoided.Large changes occur in the separate lift and drag at maximum lift/drag ratio and these have to be made compatible with the weight and thrust capacity of the configurations. The maximum lift/drag ratio of a duct can be improved by the addition of wings, especially for a duct with poor lift/drag ratio, but the best overall performance is with a duct of good lift/drag ratio and low drag.It is anticipated that impact theory underestimates the pressure forces, and hence the lift/drag ratios, which would obtain at finite Mach numbers but the trends with geometrical changes should be reasonably reliable.

Vortex shedding from square prisms in smooth and turbulent flows

1986 ◽  
Vol 164 ◽  
pp. 77-89 ◽  
Author(s):  
Yasuharu Nakamura ◽  
Yuji Ohya
Keyword(s):  
Flow Visualization ◽  
Turbulent Flows ◽  
Cross Section ◽  
Vortex Shedding ◽  
Large Scale ◽  
Resonant Interaction ◽  
The Other ◽  
Flow Past ◽  
Scale Turbulence ◽  
Main Effects

Visualization and measurements of velocity and pressure were made for the flow past prisms of variable length with square cross-section, placed normal to smooth and turbulent approaching flows. Square prisms shed vortices in one of the two fixed wake planes. The plane of shedding is switched irregularly from one to the other. Flow visualization confirms the two main effects of small– and large-scale turbulence on the flow past square prisms that had previously been suggested. In particular, large-scale turbulence intensifies vortex shedding from square prisms through resonant interaction, thereby reducing the base pressure considerably.

SAF file: It's really three dimensional file

2018 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
Prof. Dr. Jamal Aziz Mehdi
Keyword(s):  
Cross Section ◽  
Root Canal ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Circular Motion ◽  
Root Canal Treatment ◽  
Metal Core ◽  
Rotating Blade

The biological objectives of root canal treatment have not changed over the recentdecades, but the methods to attain these goals have been greatly modified. Theintroduction of NiTi rotary files represents a major leap in the development ofendodontic instruments, with a wide variety of sophisticated instruments presentlyavailable (1, 2).Whatever their modification or improvement, all of these instruments have onething in common: they consist of a metal core with some type of rotating blade thatmachines the canal with a circular motion using flutes to carry the dentin chips anddebris coronally. Consequently, all rotary NiTi files will machine the root canal to acylindrical bore with a circular cross-section if the clinician applies them in a strictboring manner

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