I think if surface oscillations frequencies are of the order of the boundary layer eigenfrequancies then it can take place. As for quantities they should be changed. But may be you know interesting story about original facility designed by Osborn Reynolds. Students in Manchester used this facility now and found that critical Reynolds number diminished. It was due to much more intensive traffic on Oxford road. So surface oscillations (and facility too) are very important

Rough surface texture and other parameters that can affect the flow.

Interesting, where it was about that flow can remain laminar even up to 8000 to 10000 Reynolds number when it flow through a pipe. About 2300 is theoretical limit for loose of instability. It is a property of the fluid dynamics equations. There may be some deviations in numbers due to the fact that some special conditions are not taken into account. But I cannot imagine about up to 8000 to 10000 Reynolds number because it's totally out of the phenomenon.

As concern to vibration, it can help to enforse the development of the turbulence but again turbulence means instability, loose of the uniqueness of the solution of the Navier-Stikes equations, chaotization. When the regime is laminar the vibration may cause some wavy process but not turbulence if critical Reynolds numbers are not achieved in a flow.

If Reynolds number is quite low then it won’t, but if Reynolds number is close to the transition definitely it will since it adds perturbation and it excites specific wavenumber and frequencies..

I think if surface oscillations frequencies are of the order of the boundary layer eigenfrequancies then it can take place. As for quantities they should be changed. But may be you know interesting story about original facility designed by Osborn Reynolds. Students in Manchester used this facility now and found that critical Reynolds number diminished. It was due to much more intensive traffic on Oxford road. So surface oscillations (and facility too) are very important

Indeed, a pipe flow can remain laminar up to large Reynolds numbers, provided that the perturbations that trigger the laminar-turbulent transition, such as wall roughness, pressure pulsations, pipe vibrations or oscillations due to phenomena that take place in the installation, etc., are very small or absent. Vibrations of the pipe can be regarded as perturbations (you will have moving walls) and, under certain circumstances, they can speed-up the transition to turbulence.

As for me, I have observed such kind of artificial transition to turbulence in my experiments. Development of turbulent spots and Klebanoff's vortices were observed in a plane Poiseuille and Blasius flows at low Reynolds numbers. You can read papes of me and my colleagues Koslov, Kachanov et al. To say true, the high level artificial disturbance in a laminar flow converts Poiseuille and Blasius flows in an other kind of strongly three-dimentional flow. You have to introduce sufficiently high level of an artificial disturbance in the vicinity of high shear layer.

Mr. Michael happy to hear my intuition is correct. I am thinking of making use of these phenomenon to induce turbulence and thereby aid heat transfer.

I will look into your papers.

I also wish to thank all others who conveyed their opinion, we freshers are learning and getting helped a lot.

Thank you so much.

I recommend Dr. M.P.Ramazanov comment. In fact we have together done some experiments on one possible mechanism for formation of turbulent spot by applying vibration in an laminar boundary layer and it's effect on an artificial sound puff. The results were promising and we observed the transitional flow were enhanced. So definitely vibration with certain amplitude and frequency at low Reynolds number can trigger the flow and may cause transition to turbulence.

From the perspective of nonlinear interactions and wave turbulence I'd say yes it can. The point is that any external oscillation forcing the fluid will tend to induce more nonlinear interactions between modes of oscillation the fluid, possibly through some kind of parametric resonance, if the external vibrations are random, stochastic resonance can come into play, all of this can help induce turbulence. Perhaps a more difficult question would be, can one control turbulence through external vibrations?

In the absence of seed of disturbances, flow can remain in the equilibrium state for unspecified limits. For example, there are instances of pipe flow remaining laminar up to 100000! Please read standard text books. In fact, it is on this principle that natural laminar flow wings are function at the cruise altitude (by additionally talioring the pressure gradient). At sea level, the same wing will show degraded drag values. Going by theory of receptivity and corresponding experiments, surface vibration will be the most potent trigger for transition.

Sorry for the tyop: "natural laminar flow wings function ......"

This is still an interesting and somehow open question in fluid mechanics. On a side, the exact solution of the NS equations for the flow in a pipe is valid for any Re number. The question is therefore focused on the stability of this solution and in literature there are many studies sometimes contradicting each other. Vibration is one of the external perturbation we can think of, but also sound (a perturbation in the pressure field) can induce instability. We could discuss about the roughness of the surface and so on.

Do not forget that also a numerical simulation can be problematic. A very accurate code could retain a laminar solution at very high Reynolds if a perturbation is not added.

The key is that the quadratic non linear terms in the NS equations tends to produce higher wavenumbers components (immagine to start simply with a flow having only component with k=1, it will produce k=2 and so on). Thus, we should analyse if such new higher components are counterbalanced by their dissipation in such an equilibrium that a laminar condition is substained. Otherwise, these components will be amplified and will produce a wide spectrum of wavenumbers that is nothing else that the turbulent regime.

The question brings me back to my master thesis, about 53 years ago.

I was checking if viscoelastic fluids delayed the onset of turbulence in the flow through round pipes. But let us go to your question, which I assume relates to newtonian fluids.

I was repeating the Newton's experiment also with water (newtonian fluid) and a carefully designed bellmouth at the pipe entrance.

In my apparatus, with very low disturbances, my critical Reynolds number (transition from laminar to turbulent flow) turned out to be about 14,000. And this was found also by changing the pipe diameter.

I was really surprised because also I knew the magic value of 2300. But looking at the literature, I found that, by carefully avoiding all possible disturbances, people had reached Reynolds number as high as 1,000,000 still having laminar flow through the pipe. Sorry, but I do nit remember the reference.

But coming to your question, I found also that, if I was running my test, e.g. at a Reynolds number of 8,000 with laminar flow in the pipe, and a big truck passed by my lab, the flow suddendly turned from laminar to turbulent. This further testifies that disturbances are important. Another conclusion is that 2300 is generally valid for industrial situations.

As far as your question:

If so can we use that to induce turbulence and enhance heat transfer?

I would say that this can be done if your system is working below the critical Reynolds number and, in any case, you can make use of turbulizers,

which is one of the main issues for enhancing heat transfer.

Best regards and good luck for your work

Dear sir

Thanks for sharing your expertise in this field. It was really informative.

Dear Jubin V Jose

In addition, I must inform you that flows in micro-channels (passive micromixers and microreactors) are in the laminar regime (low Re values) due to the sub-millimeter dimension of channels but mixing is achieved/enhanced by turbulence created by colliding fluid streams, flow past bends, rough channels and twists.

Cheers and kind regards!

Dear Jubin V Jose

Im still a student. Please correct if im wrong. It is possible to induce turbulence in laminar flow through vibration. From chemical engineering perspective, the water is made up of several molecule that bind by hydrogen bond either weak or strong will affect the frequency. This vibrational band has also contribute to its (water) properties for ability to absorb UV, microwave, electromagnetic and infrared. Hope it helps.@

Depends on the original laminar flow Reynolds number and on a Reynolds nimber created by the vibration.

Yes but depend on vibration amplitude and frequency

I agree with Dr. Abdullah and Dr. Liberzon. In fact experiments on vibrating ribbon on flat plate by me and few researchers show this could enhance formation of turbulent spot which eventually leads to turbulent boundary layer.

Turbulence and tripping from laminarity is a beast of a subject. How large will the vibrations be in amplitude? You then get into topic of bypass v/s natural transition (i.e. small fluctuations, linear growth, etc.) . There is also point of neutral curves, forcing at the appropriate Reynolds number, location, frequency-parameter space etc. Then resonance mechanisms too between naturally occurring eigenmodes of the boundary-layer system. there are also topics of super-critical and sub-critical transition. Pipe flows are a separate beast too. Issues of surface roughness, turbulence fluctuations etc. etc. etc. Initial conditions and how one sets up the experiment is the key into what one wants to observe in the experiment, as nature has a rich structure many routes available to it, as indeed do Navier-Stokes equations too. Look into Reynolds famous experiments on pipe flows.

Our recent reported results show that a trace amount of transverse vibration is good enough to trigger transition. However, in-plane vibration is less effective. See the paper:

Article The three-dimensional impulse response of a boundary layer t...

Indeed a very rich subject. Specially, experiments and high accuracy computations requires extreme caution. Some new beginning has been made in the above, explaining the dynamics of wall excitation.