The Resistance to Rotation of Free and Enclosed Disks

A general analysis of the resistance to rotation of disks at high Reynolds numbers is presented. The theoretical calculations of the fluid-induced torque on free and enclosed, smooth and rough disks, as well as torque induced by the dilute polymer solutions, are found to be in good agreement with experimental results.

Download Full-text

The Importance of Secondary Shedding in Two-Dimensional Wake Formation at Very High Reynolds Numbers

Aeronautical Quarterly ◽

10.1017/s0001925900009355 ◽

1982 ◽

Vol 33 (2) ◽

pp. 105-123 ◽

Cited By ~ 5

Author(s):

P.K. Stansby ◽

A.G. Dixon

Keyword(s):

Vortex Method ◽

Reynolds Numbers ◽

Discrete Vortex ◽

Pressure Distributions ◽

Pressure Fields ◽

High Reynolds Numbers ◽

First Approximation ◽

High Reynolds ◽

Very High ◽

Good Agreement

SummaryUncertainties in the use of the discrete-vortex method in modelling the time development of the wake of a circular cylinder at very high Reynolds numbers are investigated. It is shown that simply introducing vorticity at generally accepted separation positions at a rate of ½Us2, Us being the velocity at separation, gives wholly unrealistic wake predictions. In the base region pressure fields occur which would promote separation in steady flow and so a first approximation for ‘secondary’ separation is incorporated into the model. This brings pressure distributions and vorticity structures at subcritical and supercritical Reynolds numbers into good agreement with experiment. The convection of the vortices is calculated using the cloud-in-cell technique and comparisons are made with direct summation methods.

Download Full-text

Literature review and experimental results for a cylinder with perforations and protrusions at high Reynolds numbers

10.2514/6.1987-1388 ◽

1987 ◽

Cited By ~ 1

Author(s):

G. JONES ◽

T. HORVATH ◽

P. STAINBACK ◽

W. BEASLEY ◽

R. MCGHEE

Keyword(s):

Literature Review ◽

Reynolds Numbers ◽

Experimental Results ◽

High Reynolds Numbers ◽

High Reynolds

Download Full-text

The Effects of Polymer Solution Preparation and Injection on Drag Reduction

Journal of Fluids Engineering ◽

10.1115/1.1905644 ◽

2005 ◽

Vol 127 (3) ◽

pp. 536-549 ◽

Cited By ~ 6

Author(s):

R. Sun Chee Fore ◽

J. Szwalek ◽

A. I. Sirviente

Keyword(s):

Drag Reduction ◽

Polymer Solution ◽

Mass Production ◽

Polymer Solutions ◽

Cost Effective ◽

Reynolds Numbers ◽

Polymer Flow ◽

High Reynolds Numbers ◽

Solution Preparation ◽

High Reynolds

The understanding of drag reduction by injection of polymer solutions requires an adequate and accurate polymer solution preparation process as well as a thorough understanding of the effects that the delivery system might have on the polymer flow. Mass production of polymer solutions for engineering applications could be more cost effective if large batches of highly concentrated polymer solutions are prepared and then diluted to the final concentrations of interest. However, as shown in this study, depending on the type of polymer used this procedure might be more or less adequate. This study also corroborates that the presence of macro-molecular polymer structures induced by injecting highly concentrated polymer solutions into a shear flow translates into a drag increase and substantial degradation endurance especially at high Reynolds numbers in comparison to homogeneous polymer solutions.

Download Full-text

Numerical Simulations of Flow Around Wall-Mounted Square and Trapezoidal Structures at High Reynolds Numbers

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4047541 ◽

2020 ◽

Vol 143 (1) ◽

Author(s):

Martin Andersen ◽

Guang Yin ◽

Muk Chen Ong

Keyword(s):

Turbulence Model ◽

Reynolds Numbers ◽

Navier Stokes ◽

Freestream Velocity ◽

High Reynolds Numbers ◽

Sst Turbulence Model ◽

Layer Flow ◽

High Reynolds ◽

Two Sides ◽

Good Agreement

Abstract In the present study, flow around symmetric trapezoidal wall-mounted structures with different slope angles of the two sides subjected to a boundary layer flow at Reynolds numbers of 1.19 × 105 and 1 × 106 (based on the height of the structures and the freestream velocity) is investigated using two-dimensional (2D) Reynolds-averaged Navier–Stokes (RANS) equations combined with the k − ω shear stress transport (SST) turbulence model. It is found that the drag coefficient of the wall-mounted square structures using the k − ω SST turbulence model is in good agreement with the available published experimental data. The effects of slope angles of the two sides on the hydrodynamic quantities and the flow fields around the structures have been investigated.

Download Full-text

Development of High Accurate Flow Nozzle for Feedwater Flowrate Measurement in Nuclear Power Plant

Volume 2A: Thermal Hydraulics ◽

10.1115/icone22-30482 ◽

2014 ◽

Author(s):

Noriyuki Furuichi ◽

KarHooi Cheong ◽

Yoshiya Terao ◽

Shinichi Nakao ◽

Keiji Fujita ◽

...

Keyword(s):

Reynolds Number ◽

Nuclear Power ◽

Discharge Coefficient ◽

Reynolds Numbers ◽

Experimental Results ◽

Number Range ◽

Discharge Coefficients ◽

High Reynolds Numbers ◽

High Reynolds ◽

Extrapolation Error

The high accurate throat tap flow nozzle with four different diameter taps is developed and its discharge coefficients are measured in the Reynolds number range from 1.5×106 to 1.4×107 using the high Reynolds calibration facility of AIST,NMIJ. The discharge coefficient of a throat tap nozzle extrapolated according to ASME PTC 6 are confirmed to deviate 0.37% at Red=1.4×107 from the experimental results. The high accurate flow nozzle developed can reduce this extrapolation error of the discharge coefficient to high Reynolds numbers by using the equations of discharge coefficients, which is determined as a function of Reynolds number and tap diameter based on the experimental results of four different diameter taps. The error of extrapolated discharge coefficient using the derived equations is estimated to be less than 0.1% at Red=1.4×107. The present results show that the throat tap flow nozzle developed is expected to work as a high accurate flowmeter even under the extrapolation of the discharge coefficient toward high Reynolds numbers.

Download Full-text

A Numerical and Experimental Study of the Aerodynamics and Stability of a Horizontal Parachute

ISRN Aerospace Engineering ◽

10.1155/2013/320563 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

Mazyar Dawoodian ◽

Abdolrahman Dadvand ◽

Amir Hassanzadeh

Keyword(s):

Experimental Study ◽

Reynolds Number ◽

Numerical Simulations ◽

Drag Coefficient ◽

Reynolds Numbers ◽

Flow Conditions ◽

High Reynolds Numbers ◽

High Reynolds ◽

The Stability ◽

Good Agreement

The flow past a parachute with and without a vent hole at the top is studied both experimentally and numerically. The effects of Reynolds number and vent ratio on the flow behaviour as well as on the drag coefficient are examined. The experiments were carried out under free-flow conditions. In the numerical simulations, the flow was considered as unsteady and turbulent and was modelled using the standard - turbulence model. The experimental results reveal good agreement with the numerical ones. In both the experiments and numerical simulations, the Reynolds number was varied from 85539 to 357250 and the vent ratio was increased from zero to 20%. The results show that the drag coefficient decreases by increasing the Reynolds number for all the cases tested. In addition, it was found that at low and high Reynolds numbers, the parachutes, respectively, with 4% vent ratio and without vent are deemed more efficient. One important result of the present work is related to the effect of vent ratio on the stability of the parachute.

Download Full-text

Mixing efficiency in run-down gravity currents

Journal of Fluid Mechanics ◽

10.1017/jfm.2016.696 ◽

2016 ◽

Vol 809 ◽

pp. 691-704 ◽

Cited By ~ 5

Author(s):

G. O. Hughes ◽

P. F. Linden

Keyword(s):

Reynolds Number ◽

Reynolds Numbers ◽

Gravity Currents ◽

Mixing Efficiency ◽

The Novel ◽

High Reynolds Numbers ◽

High Reynolds ◽

Good Agreement

This paper presents measurements of mixing efficiency of the two counter-flowing gravity currents created by symmetric lock exchange in a channel. The novel feature of this work is that the buoyancy Reynolds number of the currents is higher than in previous experiments, so that the mixing is not significantly affected by viscosity. We find that the mixing efficiency asymptotes to 0.08 at high Reynolds numbers. We present a model of the mixing based on the evolution of idealized mean profiles of velocity and density at the interface between the two currents, the results of which are in good agreement with the measurements of mixing efficiency.

Download Full-text