\(\frac{d^2 y}{d x^2}\) will have dimensions of \(\frac{y}{x^2}\)

\(y \rightarrow\) pressure, \(x \rightarrow\) velocity gradient

\(x \rightarrow \frac{V}{L} \Rightarrow \frac{ LT ^{-1}}{ L } \Rightarrow T ^{-1}\)

\(\frac{y}{x^2}=\frac{ ML ^{-1} T ^{-2}}{ T ^{-2}} \Rightarrow\left[ ML ^{-1}\right]\)