Rudolph J. Swigart Cross-Hatching Studies
Experimental Studies
Canning et al.
Larson and Mateer
Mirels
Laganelli and Nestler
Cross-hatching should not exist in subsonic flow, results from intersection of Mach cones
Supersonic flow, thin turbulent boundary layer are necessary
Patterns occur in 2-D flow and axisymmetric flow
Increasing ablation results in grooves
considered char-forming materials, subliming ablator (epoxy resin), melting ablator (Teflon and Lexan)
indicate transitional/turbulent is necessary
Persen
used hydraulic analogy, consistent results with Laganelli and Nestler
Laganelli and Zempel
investigate the effect of surface disturbances on cross-hatched, disturbances only affected pattern locally but did not govern overall pattern development
William
obtained cross-hatched through ablation by sublimation
Theoretical Studies
Vortex Mechanism
Tobak
use results of linearized wing theory, pressure distribution results in surface pattern
Persen
observed that cross-hatched patterns superposed over longitudinal striations
Stock and Ginoux
concluded that streamwise vortices not necessary for cross-hatching to occur
Differential Ablation Mechanism, based on occurrence of patterns in subliming materials
Steady approach
Inger
Considered boundary layer of inviscid outer flow and viscous sublayer, Only 2-D flow past a wavy wall
analysis accurately predict temperature distribution over wavy wall, but fairly accurate in pressure distribution at transonic Mach
Conrad, Donaldson and Snedeker
considered 3-D problem,assumed heat transfer is proportional to pressure
useful for predicting a preferred wave angle
Unsteady approach
Lew and Li
considered problem of sublayer driven by outer inviscid flow perturbed by 3-D wavy wall
Lees and Kubota
investigated subliming ablator problem
Lane and Ruger
found no regions of instabilities at wavelength for Teflon, camphor and ammonium chloride
Liquid Layer Mechanism, stability of thin liquid layer
Nachtsheim
neutral stability cannot obtained in absence of surface tension
Ko
results similar to Nachtsheim
Nayfch and Saric
developed pertubation solution
Lane and Ruger
found surface tension has insignificant role in determining stability boundary
Nachtsheim and Hagen
concluded that ablation is not essential for formation of cross-hatched pattern
Surface Deformation Mechanism
Probstein and Gold
postulated that cross-hatching is the result of differential deformation due to relaxation and creep within material
Stock and Ginoux
observed very little abation but cross-hatched patterns are developed, ablation viscosity and resistivity are important parameter
Key factors to Development of Cross-Hatching
Supersonic Flow
Turbulent boundary layer
Thin boundary layer
Ablative material
Subliming material
Deformable material
Longitudinal Vorticity
Heat conduction
Liquid layer surface tension
Pressure and heat transfer distributions
Mass/weight loss
Melt-layer viscosity