DPM, as suggested by its acronym, injects a discrete mass flow rate (this is not equivalent to m_dot=rho*vel*Area). In Fluent the discrete mass flow rate of particles nis nothing but m_dot=# particles per sec [#/s] * mass of particle [kg]. The first item is known as the strength and is nothing but the reciprocal of your particle injection time step, this way you inject a single particle each time step, or better said, one parcel. Please note, there is no velocity here yet. So you need to further specify your injection velocity, and of course to specify your particle diameter or size distribution, density, etc..nHope this helpsn