It is a well known fact Turbulence is a multi-scale and non-local phenomenon Resolving all the temporal-spatial scales implies non-locality is implicitly addressed by subsequent resolution of local dynamics. However, if only temporal averaged fields are considered, then it becomes important to address non-locality explicitly. Hence, we introduce Fractional derivatives, which are non-local operators to model turbulence. It is to be noted that, the near wall region (or any viscous dominated region) tends to be local, in contrast to fully turbulent regions which are non-local. This duality of local and nonlocal dynamics is very well addressed with variable-order fractional derivatives. Its application to Couette, Pipe and Channel flow will be discussed in this talk.