![]() ![]() The reason why is that the importance of viscosity within a fluid is not determined by, In our everyday experiences with water it appears to be inviscid, however this is not always the case. Outside of the boundary layer, which is usually where the majority of the fluid lies, viscosity is negligible. This region where viscosity is important is called a boundary layer. These results should help to improve the understanding of transitions in the flow through a pipe with twisted tape insert.In many fluid dynamical models we are justified in neglecting viscosity since it is only influential in a thin region near solid objects. This causes the vorticity shedding in the flow, and hence, the fluctuations in the velocity. Beyond critical Reynolds number, the vorticity pumped from boundary layer into the shear layer is high and diffusion is not sufficient to transport the vorticity and hence the convection of vorticity sets in. It is further observed through the vorticity contours that, at low Reynolds number, the rate of vorticity generation is low and this vorticity is transported by mere diffusion. It is noticed that the Hopf bifurcation occurs three times as flow changes from steady laminar to chaotic flow. These transitions have been obtained through a bifurcation analysis of instantaneous streamwise velocity signals captured at a point where maximum fluctuations are likely to occur. Further, for 1263 ≤ Re ≤ 1400, the flow transits to chaotic behavior. For 1126 ≤ Re ≤ 1263, the flow behavior is quasi-periodic in nature and the time series of streamwise velocity shows two incommensurate frequencies namely primary and secondary frequencies with harmonics in the form of linear combination of primary and secondary frequencies. During this flow regime, the flow occurs with sinusoidal variation of streamwise velocity which exhibit single frequency in the flow. It is observed that the flow is steady laminar for Re ≤ 700 and changes to periodic laminar flow for 700 ≤ Re ≤ 1126. The results obtained with large eddy simulations (LES) of such a flow are used in the present work to explore the transitions in the flow through a pipe with twisted tape insert. This problem has been studied numerically for H/D = 8.0 and 700 ≤ Re ≤ 1400, where H is the pitch of the twisted tape, D is the diameter of the pipe, and Re is the Reynolds number based on the pipe diameter. Understanding of the transitions of such a swirling flow is an important fluid flow problem. Insertion of twisted tape in a pipe provides heat transfer augmentation due to swirl formation inside the pipe. Journal of Verification, Validation and Uncertainty Quantification.Journal of Thermal Science and Engineering Applications.Journal of Offshore Mechanics and Arctic Engineering.Journal of Nuclear Engineering and Radiation Science.Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems.Journal of Nanotechnology in Engineering and Medicine.Journal of Micro and Nano-Manufacturing.Journal of Manufacturing Science and Engineering.Journal of Engineering Materials and Technology.Journal of Engineering for Sustainable Buildings and Cities.Journal of Engineering for Gas Turbines and Power. ![]() Journal of Engineering and Science in Medical Diagnostics and Therapy.Journal of Electrochemical Energy Conversion and Storage.Journal of Dynamic Systems, Measurement, and Control. ![]()
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