Figure 7.

Neutral stability curves (NSC), indicating the range of unstable wavenumbers for particular (ω,ϕ) combinations: non-zero length ranges indicate the possibility of autoaggregation from the USS. (a) Zero population growth (ρ = 0), for three choices of α. (b) Logistic population growth (ρ = 1), for three choices of α. Under zero population growth a non-zero length range is found for all (ω,ϕ) combinations, although of restricting length as these parameters increase. Including population growth leads to a critical threshold, such that for large flow/rheotaxis autoaggregation is suppressed. Non-specified parameters are δ = 1 and U = 0.05.