scholarly journals Investigation on the drag coefficient of supercritical water flow past sphere-particle at low reynolds numbers

2017 ◽  
Vol 21 (suppl. 1) ◽  
pp. 217-223 ◽  
Author(s):  
Zhenqun Wu ◽  
Hui Jin ◽  
Leijin Guo
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Fluidized Bed ◽  
Water Flow ◽  
Supercritical Water ◽  
Single Particle ◽  
Ambient Conditions ◽  
Particle Cluster ◽  
Drag Coefficients ◽  
Flow Past

Supercritical water fluidized bed is novel reactor for the efficient gasification of coal to produce hydrogen. The Euler-Euler and Euler-Lagrange methods can be used to simulate the flow behaviors supercritical water fluidized bed. The accuracy of the simulated results with the two methods has a great dependence on the drag coefficient model, and there is little work focused on the study on particle?s drag force in supercritical water. In this work, the drag coefficients of supercritical water flow past a single particle and particle cluster. The simulated results show that the flow field and drag coefficient of single particle at supercritical condition have no difference to that at ambient conditions when the Reynolds number is same. For the two-particles model, a simplification of particle cluster, the drag coefficients of the two particles are identical at different conditions for the same Reynolds number. The variation characteristics with the Reynolds number and particles? positions are also same.

scholarly journals Investigation on drag coefficient of supercirtical water cross-flow past cylinder biomass particel at low Reynolds numbers

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 383-389 ◽  
Author(s):  
Zhen-Qun Wu ◽  
Hui Jin ◽  
Yi-Fei Ren ◽  
Lie-Jin Guo
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Fluidized Bed ◽  
Supercritical Water ◽  
Cross Flow ◽  
Euler Method ◽  
Gas Production ◽  
Viscous Drag ◽  
Force Model ◽  
Two Phase

The supercritical water gasification of biomass technology is a promising approach for the efficient and clean conversion of wet-biomass to hydrogen-rich gas production. Many of the biomass materials are of rodlike shape and gasified in supercritical water fluidized bed. So the particle-fluid two-phase flow behaviors insider supercritical water fluidized bed are of great importance. Constrained by the extreme operating condition, numerical methods, such as the Euler-Euler method and Euler-Lagrange method, are used to study the flow behaviors inside the supercritical water fluidized bed. As the accuracy of these methods are depended on the drag force model and there is little investigation on that at supercritical condition, this work is focused on the drag coefficient of cylinder biomass particle with different ratio of length to diameter. The simulated results show that there is no differ- ence for the drag coefficient of a certain particle at different condition when the Reynolds number is same. The variation tendency of the pressure and viscous drag coefficient with Reynolds number and the ratio of length to diameter is also given in this paper.

CFD Analysis of Drag Coefficient of a Parachute in a Steady and Turbulent Condition in Various Reynolds Numbers

2009 ◽  
Author(s):  
Muhammad Javad Izadi ◽  
Mazyar Dawoodian
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Aerospace Industry ◽  
Reynolds Numbers ◽  
Cfd Analysis ◽  
Drag Coefficients ◽  
Turbulent Condition ◽  
General Variation

Study of parachutes is very important in aerospace industry. In this research, the effect of various Reynolds numbers on a parachute with a vent and without a vent at the top on drag coefficient in a steady and turbulent condition is studied. After a complete research on an efficient grid study, the drag coefficients are calculated numerically. The Reynolds number is varied from 78000 to 3900000 (1 m/s to 50 m/s). It is found that, for a parachute without a vent at the top, as the Reynolds number is increased from 78000 to 800000, the drag coefficient is decreased from about 2.5 to 1.4, and then as the Reynolds number is increased to 1500000, the drag coefficient increased to about 1.62 and it stayed constant for higher Reynolds number up to 3900000. As the vent ratio of the parachute is increased from zero to 5 percent of the parachute inlet diameter, the drag coefficient increased and for further increase of the vent ratio diameter, the drag coefficient decreased, but the general variation of drag coefficient was the same as of same parachute with no vent.

The effects of surface roughness and tunnel blockage on the flow past spheres

1974 ◽  
Vol 65 (1) ◽  
pp. 113-125 ◽  
Author(s):  
Elmar Achenbach
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Drag Coefficient ◽  
Critical Reynolds Number ◽  
Measurement Techniques ◽  
Flow Conditions ◽  
Number Range ◽  
Flow Past ◽  
Reynolds Number Range ◽  
Shedding Frequency

The effect of surface roughness on the flow past spheres has been investigated over the Reynolds number range 5 × 104 < Re < 6 × 106. The drag coefficient has been determined as a function of the Reynolds number for five surface roughnesses. With increasing roughness parameter the critical Reynolds number decreases. At the same time the transcritical drag coefficient rises, having a maximum value of 0·4.The vortex shedding frequency has been measured under subcritical flow conditions. It was found that the Strouhal number for each of the various roughness conditions was equal to its value for a smooth sphere. Beyond the critical Reynolds number no prevailing shedding frequency could be detected by the measurement techniques employed.The drag coefficient of a sphere under the blockage conditions 0·5 < ds/dt < 0·92 has been determined over the Reynolds number range 3 × 104 < Re < 2 × 106. Increasing blockage causes an increase in both the drag coefficient and the critical Reynolds number. The characteristic quantities were referred to the flow conditions in the smallest cross-section between sphere and tube. In addition the effect of the turbulence level on the flow past a sphere under various blockage conditions was studied.

Flow past a flat plate at low Reynolds numbers

1958 ◽  
Vol 3 (4) ◽  
pp. 329-343 ◽  
Author(s):  
E. Janssen
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Flat Plate ◽  
Truncation Error ◽  
Reynolds Numbers ◽  
Experimental Result ◽  
Total Drag ◽  
Low Reynolds Numbers ◽  
Flow Past ◽  
The Difference

The flow past a flat plate at Reynolds numbers in the range 0·1 to 10·0 is investigated by an analogue method. The solution gives the stream function and the vorticity in the flow field surrounding the plate. From these are obtained the local coefficient of friction, the pressure distribution along the plate, and the total drag coefficient. The drag coefficient approaches the analytical values of Haaser (1950) and of Tomotika & Aoi (1953) as the Reynolds number decreases toward 0·1. The drag coefficient approaches the Blasius solution as the Reynolds number increases. At Reynolds number 10·0 the drag coefficient is still above the Blasius value, but is below the value obtained experimentally by Janour (1951). The difference from the experimental result is attributed for the most part to truncation error.

The predominant frequency for viscous flow past two tandem circular cylinders of different diameters at low Reynolds number

2019 ◽  
Vol 234 (2) ◽  
pp. 534-546
Author(s):  
Ming-ming Liu
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Viscous Flow ◽  
Lift Coefficient ◽  
Circular Cylinders ◽  
Predominant Frequency ◽  
Flow Past ◽  
Gap Ratio ◽  
The Mean ◽  
Different Diameters

Viscous flow past two circular cylinders in tandem arrangement is numerically investigated at a typical Reynolds number of 200 which is based on the diameter of the downstream cylinder. The non-dimensional diameter of the downstream cylinder D is fixed to be 1.0, while the non-dimensional diameter of the upstream cylinder d varies from 0.1 to 1.0 with an interval of 0.1. Moreover, the minimal non-dimensional distance between the two cylinders changes from 0.1 to 4.0. The numerical results show that continuous variation of the mean drag coefficient, the lift coefficient, and the lift frequency is observed with the increase in the gap ratio for d/ D = 0.1 and 0.2. Discontinuities are found for the mean drag coefficient, the lift coefficient, and the lift frequency of the downstream cylinder with the increase in gap ratio for d/ D = 0.9 and 1.0. Multiple lift oscillating frequencies of the downstream cylinder can be detected for d/ D = 0.3–0.8 at special gap ratios. Special attention is paid on d/ D = 0.4, which is a typical example for d/ D = 0.3–0.8. The predominant lift frequency of the downstream cylinder is observed to change from fL-1 to fL-2 as the increase in the gap ratio for d/ D = 0.4, which have not been previously detected. However, the predominant drag frequency of the downstream cylinder is found always to be fD-3 in present investigation scope. Moreover, a conclusion that fD-3 =  fL-1 +  fL-2 can be obtained.

scholarly journals Normal and Tangential Drag Forces of Nylon Nets, Clean and with Fouling, in Fish Farming. An Experimental Study

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2238
Author(s):  
Yarko Niño ◽  
Kevin Vidal ◽  
Aldo Tamburrino ◽  
Luis Zamorano ◽  
Juan Felipe Beltrán ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Drag Force ◽  
Fish Farming ◽  
Operating Conditions ◽  
Relevant Parameter ◽  
Sea Lion ◽  
Drag Coefficients ◽  
Average Value ◽  
Drag Forces

Experiments in a laboratory tank have provided measurements of the normal and tangential drag forces exerted on flat nets for different flow conditions. From those forces, normal and tangential drag coefficients of the nets have been obtained as functions of the Reynolds number and the solidity index. The experiments used two types of nets employed in the operation of a cultivation center: the fish net and the sea lion net, for the clean situation and for real operating conditions, with fouling adhered to the nets. Polyethylene ropes were used to characterize the presence of fouling in the nets. The experiments were carried out to determine equations for the normal and tangential drag coefficients. For the normal drag coefficient, the equations are linear with the Reynolds number, and the coefficients of the equations are linear with the solidity index. The equations are not so accurate for the tangential drag coefficient. The Reynolds number is not a relevant parameter for this coefficient and neither is the solidity index for the fish net, but the coefficient grows slightly with it for single and double sea lion nets with fouling. The literature review on the drag forces of nets reports that the tangential drag force is around 30% of the normal drag force. This value is approximately an average value of the ratio for the sea lion net and is higher for the clean fish net in this article.

scholarly journals A Wind Tunnel Investigation into the Aerodynamics of Lobed Hailstones

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 494
Author(s):  
Alexander Theis ◽  
Stephan Borrmann ◽  
Subir Kumar Mitra ◽  
Andrew J. Heymsfield ◽  
Miklós Szakáll
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Kinetic Energy ◽  
Drag Coefficient ◽  
Numerical Models ◽  
Complex Surface ◽  
Experimental Investigations ◽  
Fall Velocity ◽  
Drag Coefficients ◽  
Destructive Potential

The complex surface geometries of hailstones affect their fall behavior, fall speeds, and growth. Systematic experimental investigations on the influence of the number and length of lobes on the fall velocity and the drag coefficient of hailstones were performed in the Mainz vertical wind tunnel to provide relationships for use in numerical models. For this purpose, 3D prints of four artificial lobed hailstone models as well as spheres were used. The derived drag coefficients show no dependency in the Reynolds number in the range between 25,000 and 85,000. Further, the drag coefficients were found to increase with increasing length of lobes. All lobed hailstones show higher or similar drag coefficients than spheres. The terminal velocities of the the hailstones with short lobes are very close to each other and only reduced by about 6% from those of a sphere. The terminal velocities from the long lobed hailstones deviate up to 21% from a sphere. The results indicate that lobes on the surface of hailstones reduce their kinetic energy by a factor of up to 3 compared to a sphere. This has important consequences for the estimation of the destructive potential of hailstones.

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