The two-dimensional incompressible Newtonian flows passing an isosceles triangular prism were numerically investigated at low Reynolds numbers

which were defined with the base length. Two geometrical orientations of the prism were used the upwind arrangement (apex facing the flow) and the backwind arrangement (base facing the flow). This revealed that for large aspect ratio of the cross section

the upwind arrangement was prone to be unsteady than the backwind arrangement at the same Reynolds numbers

hence suffering transverse force but with relatively smaller drag coefficient which can be reduced by at most 19.4% when Reynolds numbers was 160. In addition

the Reynolds number effects on the lift coefficient

drag coefficient and vortex-shedding frequency of the prism at different aspect ratios were discussed for the two arrangements as well.