Consider the Reynolds Transport theorem: \frac{D B_{\text {eys }}}{D t}=\frac{\partial}{\partial t} \int_{c v} \rho b d \Omega+\oint_{c s} \rho b \overline{\mathbf{v}} \cdot \overline{\mathbf{n}} d A Which term describes a vector

that is orthogonal to the control surface?