Article records
https://feeds.library.caltech.edu/people/Liepmann-H-W/article.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenThu, 30 Nov 2023 18:11:38 +0000A Dewpoint Meter Using Cooling by Expansion of CO2
https://resolver.caltech.edu/CaltechAUTHORS:LIErsi45
Authors: Liepmann, K.; Liepmann, H. W.
Year: 1945
DOI: 10.1063/1.1770319
For use in certain aerodynamical problems a dewpoint meter using the Joule-Thompson effect, with CO2 as cooling agent, has been developed. The instrument described here has some advantages over the common instrument which depends oupon the evaporation of ether. Two slightly different devices have been used successfully.https://authors.library.caltech.edu/records/fxwkt-4fp96The Interaction Between Boundary Layer and Shock Waves in Transonic Flow
https://resolver.caltech.edu/CaltechAUTHORS:20230309-962584000.1
Authors: Liepmann, Hans Wolfgang
Year: 1946
DOI: 10.2514/8.11473
Experiments of transonic flow past a circular arc profile show that the shock-wave pattern and the pressure distribution are strongly dependent upon the state of the boundary layer. A change from laminar to turbulent boundary layer at a given Mach Number changes the flow pattern considerably.
Shock waves can interact with the boundary layer in a manner similar to a reflection from a free jet boundary. These shock waves are not distinctly discernible from pressure distribution measurements.https://authors.library.caltech.edu/records/pzsxd-srp07Magnetically driven cylindrical shock waves
https://resolver.caltech.edu/CaltechAUTHORS:LIEpof61
Authors: Liepmann, H. W.; Vlases, G.
Year: 1961
DOI: 10.1063/1.1706428
Nearly every experiment on shock-wave propagation uses plane waves. Cylindrical and spherical waves are more difficult to produce, usually decay fast and do not offer any particular advantages. In magneto-fluid dynamics, however, it is possible to produce cylindrical waves easily and the axisymmetric geometry is a natural choice to study motion across magnetic field lines.https://authors.library.caltech.edu/records/0t38w-km896A 17-inch Diameter Shock Tube for Studies in Rarefied Gasdynamics
https://resolver.caltech.edu/CaltechAUTHORS:20130509-141109412
Authors: Liepmann, H. W.; Roshko, Anatol; Coles, Donald; Sturtevant, Bradford
Year: 1962
DOI: 10.1063/1.1746625
A shock tube for studying problems in rarefied gasdynamics is described. The motivation for operating at low density (to increase the length and time scales of certain interesting flows) and the effect of low density on the performance and design of the shock tube are discussed. In order to guarantee uniform and reproducible shock waves of moderate strength, the configuration of the tube is conventional. However, innovations are introduced (for example in the suspension, the pumping system, and the diaphragm loading and rupturing mechanism) to simplify the operation of the large facility. Care in the design of the tube as a vacuum system has resulted in a leak rate of less than 0.01 μ Hg per hour. A series of shakedown runs at relatively high pressures has shown, for example, that the reproducibility of a given shock Mach number is ±0.6%.https://authors.library.caltech.edu/records/z8ejr-5kj55Structure of a Plane Shock Layer
https://resolver.caltech.edu/CaltechAUTHORS:20120921-134953075
Authors: Liepmann, H. W.; Narashima, R.; Chahine, M. T.
Year: 1962
DOI: 10.1063/1.1706527
The structure of a plane shock wave is discussed and the expected range of applicability of the Navier‐Stokes equations within the shock layer is outlined. The shock profiles are computed using the Bhatnagar‐Gross‐Krook model of the Boltzmann equation and a uniformly converging iteration scheme starting from the Navier‐Stokes solution. It is shown that the Navier‐Stokes solution remains a good approximation in the high‐pressure region of the shock layer up to approximately the point of maximum stress for all shock strengths. In the low‐pressure region, the correct profiles deviate with increasing shock strength from the Navier‐Stokes solution. The physical significance of the kinetic model used and the relation of the present study to previous theoretical and experimental work is discussed.https://authors.library.caltech.edu/records/aq5fx-3dc35Shock Tubes in Rarefied Gas Flow Research
https://resolver.caltech.edu/CaltechAUTHORS:20130510-081002532
Authors: Coles, D.; Liepmann, H. W.; Roshko, A.; Sturtevant, B.
Year: 1968
The flow
within a shock wave is governed by the relaxation times of
the molecular degrees of freedom. Advances in shock tube
design and instrumentation have made it possible in recent
years to resolve all the relaxation times including the shortest,
corresponding to the translational degree of freedom.
The shock tube thus becomes an important tool for critical
experiments in the study of the range of applicability of the
Navier-Stokes equations and similar approximations and of
the character of solutions of the Boltzmann equation. Significant
progress has been made recently in the understanding
of the most obvious such problem, the flow within a shock in
a monatomic gas. Theory and experiment are now in substantial
agreement and the over-all process of energy exchange
is understood. Problems connected with shock wave
reflection from real walls have made progress but a host of
problems remain to be studied including surface interaction
effects. The extension of this type of shock tube research to
more complicated systems, reacting gases, gas mixtures,
and the like has begun and some progress can be reported.
Recent experimental progress is illustrated by a number of
measurements made at GALCIT in the 17- and 6-in. shock
tubes. Sophistications in shock tube design and instrumentation
will be discussed.https://authors.library.caltech.edu/records/yxtj9-f8y97Shock Tubes in Rarefied Gas Flow Research
https://resolver.caltech.edu/CaltechAUTHORS:20130509-142125916
Authors: Coles, D.; Liepmann, H. W.; Roshko, A.; Sturtevant, B.
Year: 1969
DOI: 10.1063/1.1692612
The flow within a shock wave is governed by the relaxation times of the molecular degrees of freedom.
Advances in shock-tube design and instrumentation in recent years have made it possible to resolve all the
relaxation times including the shortest, corresponding to the translational degrees of freedom. The shock
tube thus becomes an important tool for critical experiments in the study of the range of applicability of
the Navier-Stokes equations and similar approximations and of the character of solutions of the Boltzmann
equation. Significant progress has recently been made in the understanding of the most obvious such problem,
the flow within a shock in a monatomic gas. Theory and experiment are now in substantial agreement and
the over-all process of energy exchange is understood. Progress has been made in problems connected with
shock wave reflection from real walls, but a host of others remain to be studied including surface interaction
effects. The extension of this type of shock-tube research to more complicated systems, reacting gases, gas
mixtures, and the like has begun and some progress can be reported. Recent experimental progress is illustrated
by a number of measurements made in the 6- and 17-in. shock tubes at the California Institute of
Technology.https://authors.library.caltech.edu/records/fd0ez-w3x85Cryogenic shock tube
https://resolver.caltech.edu/CaltechAUTHORS:LIEpof73
Authors: Liepmann, H. W.; Cummings, J. C.; Rupert, Viviane C.
Year: 1973
DOI: 10.1063/1.1694339
Two shock tubes have been developed which allow for partial or full immersion of the test sections within a cryogenic bath. One tube is used for the study of shock-wave interactions with strong density gradients, and the other to obtain very large shock Mach numbers with ideal gas conditions in all flow regions.https://authors.library.caltech.edu/records/1gjmj-c2d02Fluid Dynamics of Liquid Helium
https://resolver.caltech.edu/CaltechAUTHORS:20120813-092543887
Authors: Liepmann, H. W.
Year: 1975
DOI: 10.1137/0128058
Liquid helium at low temperatures owes its existence to h through the zero point energy classically it should be solid. ^(4)He the common isotope, owes its peculiar behavior as a fluid to its spin and hence again to h; classically the difference between ^(3)He and ^(4)He should be trivial.
In liquid helium flow we deal with a system which still shows all the usual behavior of a liquid plus
some additional strange properties which reflect directly macroscopic quantum effects. The governing
equations of motion due largely to Landau and London are, except in their linearized form, not as well
founded and most certainly less well confirmed than one would like. Consequently, the experimental
fluid dynamicist working with helium should have a field day exploring flow problems in an atmosphere
more adventureous than with any ordinary fluid. This indeed is often the case. One does, however,
ruefully discover that some of the more interesting and significant flow configurations which one likes
to study in this strange field are by no means sufficiently well explored in the corresponding classical
cases. One therefore likes to design simple fluid flow experiments which bring out the essentially new
properties of He II and permit an experimental contribution to, or decision among, the theories of
He II flow. In this spirit, experiments associated with the propagation of shock waves in liquid helium
have been initiated at GALCIT. The design and construction of a cryogenic shock tube and its application
to liquid helium are discussed in this paper.https://authors.library.caltech.edu/records/w0051-b6b50Control of laminar-instability waves using a new technique
https://resolver.caltech.edu/CaltechAUTHORS:20120627-155913693
Authors: Liepmann, H. W.; Brown, G. L.; Nosenchuck, D. M.
Year: 1982
DOI: 10.1017/S0022112082001025
A new technique using surface-film activators has been developed to induce and control laminar-instability waves by periodic heating. A flat plate was instrumented
and installed in the GALCIT High-speed Water Tunnel with flush-mounted surface heaters and probes. Extremely two-dimensional naturally occurring Tolmien-Schlichting (TS) waves were observed along with the subsequent formation of turbulent spots. Laminar-instability waves were then excited in a controlled fashion using the surface-mounted heaters. A preliminary experiment on cancellation of
excited laminar-instability waves was carried out. Finally, turbulent spots were produced using amplitude-modulated bursts to form Gaussian TS wave packets.
Flow visualization, along with wall shear measurements, was used to infer the velocity and vorticity field near the wall.https://authors.library.caltech.edu/records/n5ref-p7d21Active control of laminar-turbulent transition
https://resolver.caltech.edu/CaltechAUTHORS:20120717-085352812
Authors: Liepmann, H. W.; Nosenchuck, D. M.
Year: 1982
DOI: 10.1017/S0022112082001037
Instability waves, commonly called T-S waves, can be introduced in a laminar boundary layer by periodic heating of flush-mounted heating elements. Experiments have demonstrated that nearly complete cancellation of a T-S wave excited in this way can be achieved by using a second downstream heating element with a suitable phase shift. As one application of the technique, a single element together with a feedback loop activated by measured wall shear stress has been used to reduce the amplitude of naturally occurring laminar instability waves. A significant increase in the transition Reynolds number has been achieved.https://authors.library.caltech.edu/records/mmvts-41k88Nonlinear Interactions in the Fluid Mechanics of Helium II
https://resolver.caltech.edu/CaltechAUTHORS:20161018-152858115
Authors: Liepmann, H. W.; Laguna, G. A.
Year: 1984
DOI: 10.1146/annurev.fl.16.010184.001035
Besides its practical importance in a host of technical applications, fluid
mechanics retains its intrinsic interest as a physical discipline. The
governing equations are nonlinear, and hence the motion of fluids
demonstrates the complexities of solution of a nonlinear field theory, a fact
that has been appreciated more and more in recent times. The most striking
manifestations of this nonlinearity are shock waves and turbulence,
corresponding to nonlinear wave and vortex interactions, respectively.https://authors.library.caltech.edu/records/shc3c-g6327