魏森贝格数（Wi）是有关黏弹性流研究的无量纲，得名自卡尔·魏森贝格，是流体弛豫时间和特定进程时间的值。例如针对简单的剪力流，魏森贝格数会缩写为Wi或We，定义为剪切速率 和弛豫时间的乘积：

因为此数字是用计算应力演变的比例而来，因此可以选择剪切速率或伸长率，或是长度尺度。

魏森贝格数类似底波拉数，在技术文档上常常造成混淆，但两者的物理论释也有所不同。魏森贝格数描述因变形后的各向异性及其方向，适用在只有简单剪力的流场，底波拉数用来描述一不均匀拉伸速度下的的流场，表示弹性能保存及消耗的速率。

The Weissenberg number (Wi) is a dimensionless number used in the study of viscoelastic flows. It is named after Karl Weissenberg. The dimensionless number compares the viscous forces to the elastic forces. It can be variously defined, but it is usually given by the relation of stress relaxation time of the fluid and a specific process time. For instance, in simple steady shear, the Weissenberg number, often abbreviated as Wi or We, is defined as the shear rate times the relaxation time