Your three step procedure is good. But I am afraid that it gives infinitely many possibilities. These are the following things that are to be considered.
The flow of the liquid ( I don't prefer using the word blood , which looks ugly ) , on to the floor that decides the forces acting on each module. Sometimes the slightest change in the input can cause a great variation in the output. See the butterfly effect.
You must consider the fluid dynamics of the liquid that play a major role. Buoyancy forces, resistance, surface tension etc., all these entities have a connection with the formation of the resultant shape. For example, if you pour a glass of water , you get another shape, if you pour a glass of honey, you get some other shape.
But anyway as per your request , I am suggestion you some algorithm that I read in my Database Administration Book. Its called Cluster Analysis . I hope that it will completely help you in clustering the particles.
I am sure that following your three way step will not yield you to a particular solution. It takes you to a infinite set of possibilities ( as shapes can be any in number ). But if you combine the Cluster Analysis with Fluid Dynamics and finally garnish the total thing with Chaotic dynamics and properties of fluid, you get the perfect and exact shape.
For that you need to consider the surface tension of the medium on which the liquid is poured. The rate of flow of liquid, initial injection velocity, viscosity and the buoyancy force offered by the medium.
Then you need to simulate the model of fluid flow, by taking the initial condition and then pop it into the fluid flow equation and then approximating the condition of the fluid after time $t$ ( with some negligible error ) . So after performing interpolation and curve fitting you get a function that approximately gives you the position of the cluster at time $t$. Then after doing that, you need to simulate the resultant positions of all clusters using the vector analysis and cancel the internal forces that are opposite.
Thats how you generate the entire model perfectly.
I hope this is helps you to some extent. Ask me for more mathematical details in case if you want.