  Near field hydrodynamic interactions are essential to determine many
important emergent behaviors observed in active suspensions, but have not been
successfully modeled so far. In this work we propose an effective model capable
of efficiently capturing the essence of the near field hydrodynamic
interactions, validated numerically by a pedagogic model system consisting of
an E. coli and a spherical tracer. The proposed model effectively captures all
the details of near field hydrodynamics through only a tensorial coefficient of
resistance, which is fundamentally different from, and thus cannot be replaced
by, an effective interaction of conservative nature. In a critical test case
that studies the scattering angle of the bacterium-tracer pair dynamics,
calculations based on the proposed model reveals a region in parameter space
where the bacterium is trapped by the spherical tracer, a phenomenon that is
regularly observed in experiments but cannot be explained by any existing
model.
