Wakes

Cracking catalysts Crack-tip shielding Crack-wake bndging Cr3Al Crambe Crambe oil Cranb erry... 

The reactors were thick-waked stainless steel towers packed with a catalyst containing copper and bismuth oxides on a skiceous carrier. This was activated by formaldehyde and acetylene to give the copper acetyUde complex that functioned as the tme catalyst. Acetylene and an aqueous solution of formaldehyde were passed together through one or more reactors at about 90—100°C and an acetylene partial pressure of about 500—600 kPa (5—6 atm) with recycling as required. Yields of butynediol were over 90%, in addition to 4—5% propargyl alcohol. 

R. D. Adams and W. C. Wake, Structural adhesive Joints in Engineerings Elsevier, New York, 1984. 

W. C. Wake, ed. yidhesion and the formulation ofA.dhesives Elsevier PubHshiag Co., New York, 1982. 

Laser Doppler Velocimeters. Laser Doppler flow meters have been developed to measure Hquid or gas velocities in both open and closed conduits. Velocity is measured by detecting the frequency shift in the light scattered by natural or added contaminant particles in the flow. Operation is conceptually analogous to the Doppler ultrasonic meters. Laser Doppler meters can be appHed to very low flows and have the advantage of sensing at a distance, without mechanical contact or interaction. The technique has greatest appHcation in open-flow studies such as the deterrnination of engine exhaust velocities and ship wake characteristics. 

Fig. 3. Flow past a circular cylinder for (a). Re < 5 where no separation is evident (b) 5 < Re < 40 and fixed vortices exist in a separation bubble or wake ...

As the Reynolds number rises above about 40, the wake begins to display periodic instabiUties, and the standing eddies themselves begin to oscillate laterally and to shed some rotating fluid every half cycle. These still laminar vortices are convected downstream as a vortex street. The frequency at which they are shed is normally expressed as a dimensionless Strouhal number which, for Reynolds numbers in excess of 300, is roughly constant ... 

Dana E. Selley Laura J. Sim Steven R. Childers Wake Forest University... 

Meteors produce atmospheric plasmas as their kinetic energy is converted to thermal energy (50). Most particles from space are consumed before they reach an altitude of 50 km. Meteors are of Httie practical use, although radio waves can be bounced off the plasmas left in their wakes (see Exthaterresthial materials). ... 

Studies of individual bubbles rising in a two-dimensional gas—Hquid—soHd reactor provide detailed representations of bubble-wake interactions and projections of their impact on performance (Fig. 9). The details of flow, in this case bubble shapes, associated wake stmctures, and resultant bubble rise velocities and wake dynamics are important in characteri2ing reactor performance (26). 

Fig. 9. Bubble-wake interactions in a gas—Hquid-soHd reactor (a) soHds concentration profile within bubble-wake domain, where A—A and B—B represent planes through the bubble, vortex, and wake (b) projected impact of interactions on reaction rate as function of particle si2e and Hquid velocity, where (—)...

L. S. Fan and K. Tsuchiya, Bubble Wake Dynamics In Tiquids andTiquid—SolidSuspensions Butterworth-Heinemaim, Boston, Mass., 1990. 

A number of mechanisms have been proposed by which this common irradiated state is obtained. The most widely accepted is the thermal spike theory, which considers the heat generated in the wake of a fast particle passing through a soHd as being sufficient to cause severe stmctural disturbances which are then fro2en in by rapid cooling. Many property changes can be explained by this theory (146). 

Solid circulation Entrainment in bubble wake Elutriation by bursting of bubbles... 

Fig. 12. Micromechanics of ductile reinforcement particles yielding within process 2one and particles bridging in crack wake.

Toughening for whisker-reinforced composites has been shown to arise from two separate mechanisms frictional bridging of intact whiskers, and pullout of fractured whiskers, both of which are crack-wake phenomena. These bridging processes are shown schematically in Figure 13. The mechanics of whisker bridging have been addressed (52). The appHed stress intensity factor is given by ... 

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