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I want to understand physical meaning and possible implications of few terms often used in physics specially with regards to gravitational waves / space-time fabric

  1. Space-time fabric is disturbed by the presence of a body. The body produces ripples which propagate like waves. Does it mean that the only way for these ripples to be formed is when an object is created (possibly from energy or from events like black holes merger etc)?

  2. If Space-time fabric is disturbed by bodies, does their movement also disturb it? Meaning, if a body moves, does it also cause ripples in the space-time fabric?

  3. If waves are induced in space-time fabric by bodies, can we expect phenomenon like "turbulence in fluid mechanics" to be present in gravitational waves too?

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Confined energy (matter) is what gravitates. You can't create or destroy energy (as far as we know). So gravitational waves can be created only when the location of that confined energy changes.

Weak gravitational waves moving through other weak fields do not affect each other, so there is no turbulence or other similar effect. However, strong waves, or weak waves moving through a strong field, will experience distortions related to the fact that the peaks represent different time rate than the troughs--which is certainly not 'turbulence'. So the answer is no, there is no turbulence. Turbulence is an effect of fluid moving through structures, not an effect of waves, anyway.

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    $\begingroup$ While searching on the subject, I stumbled upon this. Please review perimeterinstitute.ca/news/turbulent-black-holes $\endgroup$ – Mist Feb 21 '16 at 14:04
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    $\begingroup$ "Turbulence" arises in nonlinear wave equations all the time. I would be surprised is there wasn't something like turbulence in gravitational waves also. Although it may not follow Kolmogorov's hypothesis like a fluid, I would expect gravitational waves to have the same characteristics of turbulence. $\endgroup$ – tpg2114♦ Feb 21 '16 at 15:12
  • $\begingroup$ @tpg2114 For nonlinear coupling and/or turbulence to occur, the waves have to dominate the background, which is not given for gravitational waves. $\endgroup$ – AtmosphericPrisonEscape May 19 '19 at 3:16
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If one has a pair of lumps of mass, such as two parts of an ordinary body with non-zero size, or a planet near a star, or a pair of stars, then most motions of the pair of lumps will result in the emission of gravitational waves (very weak for bodies of ordinary mass). There are exceptions such as straight line motion in empty space, but motions such as oscillation and the motion when two or more bodies orbit one another usually result in the emission of gravitational waves. (These waves are of tiny amplitude so can be ignored in most circumstances). There are exceptions, such as when a motion does not change the quadrupole moment of an isolated system. In that case the main way for waves to be excited cancels itself out and the radiation, if it is there at all, is extremely feeble or zero. An example of strictly zero radiation is the case of a perfectly spherically symmetric explosion or collapse. But one does not expect to find such perfect symmetry in most processes.

Coming now to the question of turbulence, you may have in mind simply a random collection of low-amplitude waves. This is not strictly turbulence but in some respects it is like turbulence. Or you may mean complicated motion involving non-linear effects. This can happen for high-amplitude waves.

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