Bernoulli enthalpy  A fundamental concept in the theory of sound
Abstract
A completely general formulation of the theory of sound in a turbulent gas which incorporates the new concept of Bernoulli enthalpy is developed. It is shown that the source of the radiative sound field is the substantive rate of change of the Bernoulli enthalpy. Two basic conceptual issues of the modern theory of sound are resolved: the radiative sound is clearly separated from the source of sound with each part characterized by its own scalar field; and the Bernoulli source of sound is compact, i.e., it is confined to the region of rotational nonhomentropic flow. It is found that an important dipole source of the Bernoulli field can result by passing turbulence through a highly curved potential flow. The dominant source of Bernoulli enthalpy in lowspeed noncurved flows is the classic Lighthill quadrupole. An analogy between the present theory and the pseudosound concept of Ribner is given. The linear problem of sound interacting with a mean shear flow is formulated with the new theory. A numerical example is given for the case of a plane wave impinging on a Gaussian plane jet.
 Publication:

AIAA Conference on the Exploration of the Outer Planets
 Pub Date:
 March 1975
 Bibcode:
 1975aiaa.confQ....Y
 Keywords:

 Aerodynamic Noise;
 Bernoulli Theorem;
 Enthalpy;
 Gas Flow;
 Sound Fields;
 Turbulent Flow;
 Acoustic Propagation;
 Lighthill Gas Model;
 Noise Generators;
 Plane Waves;
 Potential Flow;
 Quadrupoles;
 Shear Flow;
 Sound Generators;
 Acoustics