Stress tensor in a non-viscometric flow such that the Rivlin-Ericksen tensors of order three and higher are zero

It is known that there exist viscometric and non-viscometric flows in which all Rivlin-Ericksen tensors of order three and higher are zero. From Rivli n's work, it is also known that in these flows, the stress tensor in an inc ompressible viscoelastic fluid may be expressed in terms of nine material f unctions of which five are independent. It is shown here that only six of t hese functions are required, out of which only five are again independent. The well known case of a viscometric flow can also be deduced from the six term, general expansion obtained here. (C) 1999 Elsevier Science B.V. All r ights reserved.