摘要:

Solutions of a viscoinertial western‐boundary‐layer problem arising in physical oceanography are discussed for both no‐slip and stress‐free boundary conditions. A fairly complete characterization of the behavior of the solutions in a number of regimes is presented using the techniques of regular perturbation expansion, matched asymptotic expansion, and rescaling of both regular and singular solutions. A comparison with the actual solutions found by extensive numerical computations is given. Parametrization of solutions in terms of the unknown first (or second) derivative at the origin, for which a useful analytic approximation is developed, provides a convenient characterization of the entire

ISSN:0022-2526    

DOI:10.1002/sapm19867511

年代:1986

数据来源: WILEY

摘要:

Approximations to the characteristic function of the lognormal distribution are computed and used to calculate approximations to the density of sums of lognormal random variables.

ISSN:0022-2526    

DOI:10.1002/sapm198675137

年代:1986

数据来源: WILEY

摘要:

Sound radiation by instability wavepackets evolving from general initial conditionsin a low‐Mach‐number, slightly unstable boundary layer is studied. The formulation can be viewed as an exact instance of Lighthill's [13] acoustic analogy. The original disturbance may be line‐ or point‐centered with an infinitesimal amplitude. The sound field is confined within an expanding sphere. The directivity of sound is beamed and points upstream. This “superdirectivity” is slowly enhanced in time whereas the sound level is slowly attenuated. Nonlinear processes, once they come into play, reverse the temporal behavior of the sound level and sound directivity. For the boundary‐layer profiles studied, nonlinearity causes a “burst,” in a finite time, of the sound field in the

ISSN:0022-2526    

DOI:10.1002/sapm198675157

年代:1986

数据来源: WILEY

摘要:

We consider nonlinear finite‐amplitude progressive shear‐flow waves on a basic velocity profile consisting of two coflowing layers of inviscid equal‐density fluid, each of uniform but different vorticity. The problem is formulated as a nonlinear integral equation describing the shape of the vorticity discontinuity in a frame of reference in which the flow is steady. Numerical solutions to this equation are presented for a range of values of the vorticity ratio Ω. For 1>© ≥ − 1 the theoretical maximum wave amplitude occurs when the wave crest forms a 90° corner which just touches the appropriate critical‐layer stagnation point. The linearized stability of the progressive wave states to arbitrary subharmonic isovortical disturbances is studied numerically. The results indicate stability at moderate values of the

ISSN:0022-2526    

DOI:10.1002/sapm198675177

年代:1986

数据来源: WILEY