Presence of particle clusters in gas–solid suspensions reduces the gas–particle drag force compared to a uniformly distributed suspension.

The amount of drag reduction decreases with increasing both solid-phase volume fraction and mean slip Reynolds number.

Decrease of drag reduction with increasing Reynolds number is attributed to the decrease of the Brinkman screening length.

Decrease of drag reduction with increasing volume fraction is attributed to the decrease of configurational entropy.

A drag model is proposed for clustered configurations over a range of solid-phase volume fraction and mean slip Reynolds number.