Simulation of Sphere’s Motion Induced by Shock Waves

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Dan Igra ◽  
Ozer Igra ◽  
Lazhar Houas ◽  
Georges Jourdan
Keyword(s):  
Shock Waves ◽  
Drag Coefficient ◽  
Drag Force ◽  
Stationary Flow ◽  
Experimental Results ◽  
Experimental Findings ◽  
Sphere Drag ◽  
Simulation Scheme ◽  
Good Agreement

Simulations of experimental results appearing in Jourdan et al. (2007, “Drag Coefficient of a Sphere in a Non-Stationary Flow: New Results,”Proc. R. Soc. London, Ser. A, 463, pp. 3323–3345) regarding acceleration of a sphere by the postshock flow were conducted in order to find the contribution of the various parameters affecting the sphere drag force. Based on the good agreement found between present simulations and experimental findings, it is concluded that the proposed simulation scheme could safely be used for evaluating the sphere’s motion in the postshock flow.

Shock tube study of the drag coefficient of a sphere in a non-stationary flow

1993 ◽  
Vol 442 (1915) ◽  
pp. 231-247 ◽  
Keyword(s):  
Shock Tube ◽  
Drag Coefficient ◽  
Stationary Flow ◽  
Wave Flow ◽  
High Acceleration ◽  
Wide Range ◽  
Post Shock ◽  
Exposure Holography ◽  
Sphere Drag ◽  
Tube Study

A review of previous attempts to study the drag coefficient of a sphere in a non-stationary flow, experimentally, is given. Thereafter, a detailed account of the present study is presented. A shock tube facility was used for inducing relatively high acceleration in small spheres laid on the shock tube floor. The spheres acceleration resulted from the drag force imposed by the post shock wave flow. Using double exposure holography, the spheres trajectory could be constructed accurately. Based upon such trajectories, the spheres drag coefficient was evaluated for a relatively wide range of Reynolds number (6000 < Re <101000). It was found that the obtained values for the sphere drag coefficient were significantly larger than those obtained in a similar steady flow case.

scholarly journals Preliminary study of software tracker usage to analyze inhibitory style on free fall movie events

2018 ◽  
Vol 197 ◽  
pp. 02012
Author(s):  
Seni Susanti ◽  
Ea Cahya Septia Mahen ◽  
Ade Yeti Nuryantini
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Free Fall ◽  
Force Analysis ◽  
Drag Coefficients ◽  
Drag Forces ◽  
Preliminary Study ◽  
Free Falling ◽  
Good Agreement

This paper presents drag force analysis of free falling object using software tracker. We use video cupclips that have been embedded in this software. The video featured cupcakes to which hung a number of different paper clips were dropped simultaneously. We track the trajectory of free falling cupclips using the software to get the information of position, speed, and acceleration of each cupcake against time. From the data we get the value of drag forces and drag coefficients for each time. The result shows that the drag force value increased to almost constant value, otherwise the drag coefficient is reduced to almost constant values well. According to the results, the analyzed data has good agreement with the theory. Thus, software tracker can be used as media to learn drag force easily and inexpensively.

scholarly journals Numerical Investigation of Shock Wave Diffraction over a Sphere Placed in a Shock Tube

2016 ◽  
Vol 2016 ◽  
pp. 1-5
Author(s):  
Sergey Martyushov ◽  
Ozer Igra ◽  
Tov Elperin
Keyword(s):  
Shock Tube ◽  
Drag Coefficient ◽  
Flow Model ◽  
The Body ◽  
Shock Wave Diffraction ◽  
Present Scheme ◽  
The Past ◽  
Steady Flow Condition ◽  
Experimental Findings ◽  
Good Agreement

For evaluating the motion of a solid body in a gaseous medium, one has to know the drag constant of the body. It is therefore not surprising that this subject was extensively investigated in the past. While accurate knowledge is available for the drag coefficient of a sphere in a steady flow condition, the case where the flow is time dependent is still under investigation. In the present work the drag coefficient of a sphere placed in a shock tube is evaluated numerically. For checking the validity of the used flow model and its numerical solution, the present numerical results are compared with available experimental findings. The good agreement between present simulations and experimental findings allows usage of the present scheme in nonstationary flows.

Drag coefficient of a sphere in a non-stationary flow: new results

2007 ◽  
Vol 463 (2088) ◽  
pp. 3323-3345 ◽  
Author(s):  
G Jourdan ◽  
L Houas ◽  
O Igra ◽  
J.-L Estivalezes ◽  
C Devals ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Stationary Flow ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Steady Flows ◽  
Two Phase ◽  
Spider Web ◽  
Wide Range ◽  
The Difference ◽  
Sphere Drag

The drag coefficient of a sphere placed in a non-stationary flow is studied experimentally over a wide range of Reynolds numbers in subsonic and supersonic flows. Experiments were conducted in a shock tube where the investigated balls were suspended, far from all the tube walls, on a very thin wire taken from a spider web. During each experiment, many shadowgraph photos were taken to enable an accurate construction of the sphere's trajectory. Based on the sphere's trajectory, its drag coefficient was evaluated. It was shown that a large difference exists between the sphere drag coefficient in steady and non-steady flows. In the investigated range of Reynolds numbers, the difference exceeds 50%. Based on the obtained results, a correlation for the non-stationary drag coefficient of a sphere is given. This correlation can be used safely in simulating two-phase flows composed of small spherical particles immersed in a gaseous medium.

Fluid Drag on a Sphere Rolling in a Tube

1967 ◽  
Vol 34 (3) ◽  
pp. 538-540
Author(s):  
A. B. Bauer ◽  
R. A. DuPuis
Keyword(s):  
Incompressible Fluid ◽  
Drag Force ◽  
Reynolds Numbers ◽  
Vertical Tube ◽  
Experimental Results ◽  
Constant Speed ◽  
Sphere Diameter ◽  
Fluid Drag ◽  
Drag Law ◽  
Good Agreement

The incompressible fluid drag force on a sphere rolling at constant speed in a closed-end tube has been analyzed for the case where the tube inside diameter is only slightly larger than the sphere diameter. One drag law is found for Reynolds numbers much less than 75π/4λ1/2, where λ is a parameter defined by the sphere and tube diameters. A second drag law is found for Reynolds numbers much larger than 75π/4λ1/2. Experimental results show good agreement with these drag laws. The first law is almost identical with the results of Christopherson and Dowson, and of McNown, et al., for a sphere falling in a vertical tube.

Study of Flow over a Step Cylinder

2009 ◽  
Vol 15 ◽  
pp. 9-14 ◽  
Author(s):  
C. Morton ◽  
S. Yarusevych ◽  
I. Carvajal-Mariscal
Keyword(s):  
Drag Coefficient ◽  
Pressure Coefficient ◽  
Numerical Approach ◽  
Experimental Results ◽  
Computational Results ◽  
Vortical Structures ◽  
Wake Vortices ◽  
Flow Development ◽  
Experimental Findings ◽  
Downstream Development

Flow over a step cylinder at ReD = 2000 and D/d = 2 was investigated using a URANS-based numerical approach. The results illustrate the downstream development and interaction of wake vortices and identify streamwise vortical structures originating at the step. The observed flow development is shown to be in agreement with experimental results. Also, a comparison of the computational results and previous experimental findings is carried out for the drag coefficient and the pressure coefficient.

Shock waves and non-stationary flow in a duct of varying cross-section

1971 ◽  
Vol 46 (1) ◽  
pp. 111-128 ◽  
Author(s):  
Naruyoshi Asano
Keyword(s):  
Shock Waves ◽  
Cross Section ◽  
Small Amplitude ◽  
Stationary Flow ◽  
Shock Propagation ◽  
Sound Waves ◽  
One Dimensional ◽  
Dimensional Approximation ◽  
Propagation Law ◽  
Good Agreement

Sound waves of finite but small amplitude propagating into a quasi-steady, supersonic flow in a non-uniform duct are analyzed by means of a perturbation method. General properties of the flow and of the wave propagation are studied using a one-dimensional approximation. A shock propagation law in the unsteady flow is obtained. As an example, the formation and development of shock waves are discussed for a duct with a conical convergence. Comparisons of the theory with an experiment are also made; fairly good agreement is found.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

PHOTOINDUCED NONLINEAR OCTUPOLAR POLARIZATION: TRANSIENT AND PERMANENT REGIMES

1996 ◽  
Vol 05 (04) ◽  
pp. 653-670 ◽  
Author(s):  
CÉLINE FIORINI ◽  
JEAN-MICHEL NUNZI ◽  
FABRICE CHARRA ◽  
IFOR D.W. SAMUEL ◽  
JOSEPH ZYSS
Keyword(s):  
Theoretical Analysis ◽  
Second Harmonic ◽  
Experimental Results ◽  
Polar Field ◽  
Rotational Spectrum ◽  
Dual Frequency ◽  
One Dimensional ◽  
Ethyl Violet ◽  
Disperse Red 1 ◽  
Good Agreement

An original poling method using purely optical means and based on a dual-frequency interference process is presented. We show that the coherent superposition of two beams at fundamental and second-harmonic frequencies results in a polar field with an irreducible rotational spectrum containing both a vector and an octupolar component. This enables the method to be applied even to molecules without a permanent dipole such as octupolar molecules. After a theoretical analysis of the process, we describe different experiments aiming at light-induced noncentrosymmetry performed respectively on one-dimensional Disperse Red 1 and octupolar Ethyl Violet molecules. Macroscopic octupolar patterning of the induced order is demonstrated in both transient and permanent regimes. Experimental results show good agreement with theory.

Numerical Studies on Trapped-Vortex Concepts for Stable Combustion

1998 ◽  
Vol 120 (1) ◽  
pp. 60-68 ◽  
Author(s):  
V. R. Katta ◽  
W. M. Roquemore
Keyword(s):  
Drag Coefficient ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Third Order ◽  
Cold Flow ◽  
Flow Simulations ◽  
Numerical Studies ◽  
Dynamic Flows ◽  
Experimental Findings ◽  
Trapped Vortex

Spatially locked vortices in the cavities of a combustor aid in stabilizing the flames. On the other hand, these stationary vortices also restrict the entrainment of the main air into the cavity. For obtaining good performance characteristics in a trapped-vortex combustor, a sufficient amount of fuel and air must be injected directly into the cavity. This paper describes a numerical investigation performed to understand better the entrainment and residence-time characteristics of cavity flows for different cavity and spindle sizes. A third-order-accurate time-dependent Computational Fluid Dynamics with Chemistry (CFDC) code was used for simulating the dynamic flows associated with forebody-spindle-disk geometry. It was found from the nonreacting flow simulations that the drag coefficient decreases with cavity length and that an optimum size exists for achieving a minimum value. These observations support the earlier experimental findings of Little and Whipkey (1979). At the optimum disk location, the vortices inside the cavity and behind the disk are spatially locked. It was also found that for cavity sizes slightly larger than the optimum, even though the vortices are spatially locked, the drag coefficient increases significantly. Entrainment of the main flow was observed to be greater into the smaller-than-optimum cavities. The reacting-flow calculations indicate that the dynamic vortices developed inside the cavity with the injection of fuel and air do not shed, even though the cavity size was determined based on cold-flow conditions.

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