A process in which force is generated within phasic smooth muscle tissue, resulting in a change in muscle geometry. Force generation involves a chemo-mechanical energy conversion step that is carried out by the actin/myosin complex activity, which generates force through ATP hydrolysis. In the phasic smooth muscle, the muscle contraction occurs without an ordered sarcomeric structure. Phasic smooth muscle contraction occurs in a series of discrete contractions and relaxations.