To start off, we ran simulations where the clusters are made with uniform particles arranged in a tightly packed lattice. The following simulation was done without adhesion. Note that the clusters are completely destroyed. Simple energy arguments can show that the clusters come in with far more kinetic energy than the gravitational potential of the small amount of mass present. As such, the clusters have no change of surviving the impact.
In here put videos for latices with adhesion.
Simulations were also done using clusters that had formed through the patch accretion simulations. The output of those simulations was run through a process to find gravitationally bound clusters. Two of those clusters were saved off and then loaded into this set of simulations.
The first round of simulations uses an impact velocity of 0.1 cm/s. The first of these had an adhesion force that was 20,000 times the force of gravity. As you can see from the video, this is not sufficient to hold the clusters together.
The second simulation increased the adhesive force to 10 million times gravity. This is large enough to hold the clusters together with some defomration at the point of contact. This might seem like an extremely large force, but adhesion is an electromagnetic force which is naturally many orders of magnitude larger than gravity.
Taking the adhesion up to 100 million times gravity gives a similar result, but with less deformation.
Increasing the impact velocity to 1 cm/s leads to needing more adhesion to hold the clusters together. The following video shows that 10 million times gravity is not sufficient to hold things together. However, while the collisions break the clusters apart, many of the resulting pieces are smaller clusters, instead of individual particles.
100 million times gravity is sufficient to hold the clusters together at 1 cm/s, as shown in the following video. A few pieces are lost during the collision, but the bulk of the material sticks together.
100 million times gravity is not sufficient at 10 cm/s. That simulation results in the clusters being destroyed. Some material manages to clump a little in the result, but not as much as the 1 cm/s collision with adhesion set to 10 million times gravity.
In order to get the particle to stick together at this speed the adhesion force needs to be 10 billion times stronger than gravity.