# particle trajectory calculation

 Register Blogs Members List Search Today's Posts Mark Forums Read

 January 8, 1999, 03:09 particle trajectory calculation #1 ursenbacher Guest   Posts: n/a Let be a particle droped in a 2D flow without speed. The speed of the flow is initialy on the x direction and then the velocity change (direction and magnitude). Is there ananlytical solution for this problem? Where can I find some references about this subject?

 January 8, 1999, 13:57 Re: particle trajectory calculation #2 John C. Chien Guest   Posts: n/a So,initially the location of the particle is known, and the relative velocity is also known and is in x-direction. From this and the particle diameter, and Reynolds number you can compute the drag force acting on the particle. ( you need this formula for drag coefficient on a sphere at different Reynolds number , and you need to do some searching to look for this formula on your own. not me!) Then you can use Newton's 2nd law to compute the particle motion for a small time step delta t. You do this for the motion in x-direction and the motion in y-direction. ( the force in y-direction is the gravitational force.) F=m*a, m is the mass of the particle, and F is the component of force in either x- or y-directions, a is the acceleration=dV / dt. Now you have dV=a*dt, you can pick a small dt to compute your dV, that is the change in velocity at the end of dt. The velocity is then V(t+dt)=V(t) + dV. At this point the particle should move to a new location defined by x(t+dt)=x(t) + V,in x-direction * dt, y(t+dt)=y(t) + V,in y-direction * dt. Since the particle will have both V,x and V,y velocity components, make sure to find the relative velocity and the direction so that the proper drag force can be computed ( this is also the direction of the relative velocity). In y-direction, the force acting on the particle is m*g + F,y . m*g is the gravitational force which is roughly constant and F,y is the component of the darg force in y-direction which depends on the relative velocity at time t and t=dt and so on..

 January 28, 1999, 17:15 Re: particle trajectory calculation #3 R.kurz Guest   Posts: n/a Here are some publications that cover the problem (I assume you are interested in the behavior of small particles): 1-Tchen,C.M. Mean Value and Correlation Problems Connected with the motion of Small particles suspended in a turbulent flow, Diss. TH Delft, 1947 2-Millikan,R.A. The general law of a small spherical body through a gas, Phys Review, Sec.Ser.,Vol. 22,No.1, 1923 3-Allen,M.D., Raabe,O.G. Re-evaluation of Millikans Oil drop datafor the motion of small particles in air, J.Aerosol Sciences, Vol13,No.6,1982 4-Kurz,R., Experimentelle und theoretische Untersuchungen an gleichfoermig und ungleichfoermig geteilten Turbinengittern, Diss UBw Hamburg, 1991. Hope this helps!

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post yueroo FLUENT 2 July 13, 2009 13:32 dm2747 FLUENT 0 April 17, 2009 01:29 steven CFX 0 July 13, 2006 17:49 AB Siemens 6 November 15, 2004 05:41 yueroo FLUENT 2 February 28, 2001 05:26

All times are GMT -4. The time now is 06:44.