Organization: Physics (PH)
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The mission of the Physics Department is to provide defense-relevant, advanced education and research programs to meet Naval unique needs, and increase the warfighting effectiveness of the U.S. Naval Forces, DoD and allied armed forces.
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Publication Lompoc Valley Diffusion Experiment analysis - Mt. Iron comparison and two zone convective scaling model(Monterey, California. Naval Postgraduate School, 1992-01) Skupniewicz, C.E.; Kamada, Ray; Drake, S.A.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); PhysicsLVDE(Lompoc Valley Diffusion Experiment) was conducted Aug 1989 to assess the potential risk of gaseous releases from the Hypergolic Stockpile and Storage Facility at Vandenberg AFB. Results of the LVDE are compared to the predictive equations of the Mt. Iron Diffusion Tests, conducted at Vandenberg in the 1960's. The Mt. Iron equation parameterizes diffusion with on-base meteorological tower input data. Regression techniques similar to those of Mt. Iron are used in this comparison, resulting in LVDE equations which use the same meteorological data as input. Instantaneous and time averaged centerline concentrations, in both flat and complex terrain are analyzed. For all cases LVDE concentrations are shown to decrease with range less rapidly than the Mt. Iron equation predicts. We suggest that this bias is due to gravitational and/or scavenging losses of the tracer material used in Mt. Iron. A 'two-zone' convective scaling equation is developed which diffuses the plume differently in cloud covered and clear sky portions of the domain. The method is shown to be superior to homogeneous convective scaling equations, and comparable to a statistical approach based on the plume measurements. While the method works for maximum concentration predictions, it fails for plume width and crosswind integrated concentration for X > 6Publication Investigation of the Effect of Convergent Detonation on Metal Acceleration and Gurney.(2012-06) Ludwig, Wibke; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); PhysicsThere are longstanding interests in the analysis of explosive effects and applications in order to derive properties and predict an explosive’s behavior. This work makes a contribution to the research field of metal acceleration by the means of detonations. The effects of both planar and convergent detonation fronts on metal acceleration are investigated with respect to the Gurney model. The derived characteristic velocity, the so-called Gurney constant, is material specific and characterizes the ability of metal acceleration for a certain explosive. The hydrocode program ANSYS AUTODYN is used to calculate and analyze the simulations of this work. The focus is set on cylinder expansion tests with respect to parametric variations. In addition, cylindrical coaxial charges are explored in order to compare the different methods of realizing a convergent detonation front. Experimental and simulated results are compared, discussed and evaluated.Publication Cerenkov and sub-Cerenkov radiation from a charged particle beam(Monterey, CA; Naval Postgraduate School, 1987) Neighbours, John R.; Buskirk, Fred R.; Maruyama, Xavier K.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Naval Postgraduate School (U.S.); PhysicsAs a consequence of the relaxation of the phasing conditions between the moving charge and radiated wave for finite beam path lengths, the Cerenkov peak is broadened and the threshold energy is developed which is applicable to charged beams consisting of single point charge or charge bunch of finite size, as well as beams consisting of periodically repeated bunchesPublication A collage of NPS Physics Department Faculty, ca. 1973(Monterey, California; Naval Postgraduate School, 1973) Buskirk, Fred R.; Cooper, John; Crittenden, Eugene; Dyer, John; Harrison, Don; Handler, Harry; Otto, Hinez; Kalembach, Sydney; Kelly, Raymond; Milen, Ed; Neighbords, John; Reese, William; Wilson, Brian; Physics (PH); Graduate School of Engineering and Applied Science (GSEAS); PhysicsPublication Basic Research in Thermoacoustic Heat Transport(Monterey, California. Naval Postgraduate School, 1996-06-11) Atchley, Anthony A.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); PhysicsThis technical report details progress in basic research in thermoacoustic heat transport made during the period June 1, 1995 through May 30, 1996. Research efforts were primarily concentrated in three areas: 1) investigation of fundamental limitations to the performance of thermoacoustic devices; 2) design, construction, and demonstration of a proof-of-concept, shipboard, heat driven thermoacoustic cooler capable of cooling loads of 1 kW; 3) measurement of transient effects in thermoacoustic devices to provide data to test nonlinear, timedependent models of thermoacoustics. Accomplishments include 1) the design of a prototype toroidal prime mover; 2) preliminary measurements of the temperature evolution along a stack in a mechanically driven configuration; 3) preliminary measurements of transient effects in prime movers; 4) preliminary design of a new prime mover configuration; and 5) fabrication of a 1 kVV heat driven cooler. A publications, patents, presentations, and honors report is also included.Publication Improved Efficiency and Power Density for Thermoacoustic Coolers(Monterey, California. Naval Postgraduate School, 1995-07-27) Hofler, Thomas J.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); PhysicsA new design for a thermoacoustic heat driven cooler is proposed and has been analyzed via a numerical model. The engine layout incorporates a half wavelength or can be run in a full wavelength with dual prime movers and dual coolers coupled thermally in parallel. Both simplified models and more physically realistic models have been constructed and adjusted for good performance. Simplified models indicate an overall COP of 0.48, which means that the total cooling power is a factor of 0.48 smaller than the total heat input. More detailed and realistic models indicate an overall COP of 0.43. Geometry numbers have been finalized and much of the drafting for an experimental unit has been completed. We hope that high power densities can be achieved with this engine. We also believe that overall COP's in the range of 0.6 to 0.7 may be possible with further improvements. Additionally, we have numerically studied issues of achieving acoustic onset with this engine and the sensitivity of the onset condition to the model parameters. We have also developed a new heat exchanger fabrication method which will allow us to achieve the smallness of geometry scale that was discussed in the previous report. The practical result is better thermal coupling with less acoustic dissipation. The fabrication method is also considerably simpler than our previous method.Publication Sea test development of laser altimeter(Monterey, California. Naval Postgraduate School, 1991-01) Crittenden, Eugene Casson; Rodeback, George Wayne; Milne, Edmund Alexander; Cooper, Alfred William; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); PhysicsLow altitude (81 m.) narrow-beam laser reflectance measurements were made from the nearly ocean-like water surface under the Golden Gate bridge. This site allowed precise measurements not possible from flying platforms. For short wavelength water waves superimposed on swell, the signal amplitude probability distribution showed periods of zero return signal, even for vertical incidence, apparently due to tipping of the average water surface. The nonzero signals show an antilog-normal probability distribution, skewed toward higher signal than that provided by a normal (Gaussian) distribution. With incidence angle displaced from the vertical, the distribution shape is retained but with more frequent zero reflections. The decrease with angle of the average signal, including the zeroes, is well fitted with a Gram-Charlier distribution, as seen by earlier observers using photographic techniques which masked these details of the structure. For the simpler wave pattern due to a long sustained wind direction, the signal amplitude probability distribution is lognormal with no zero signal periods. For this case, the distribution shifts toward exponential at large angles from the vertical. For surface states intermediate between the above two extremes the distribution is often normal. The larger return signals resulting from the skew toward larger amplitudes from lognormal are more favorable for disposable laser altimeters than previously believed. Also for an altimeter which may be swinging from a parachute or balloon, the return at angles from the vertical remains high. The presence of occasional zero return signal does degrade the accuracy of altitude somewhat for a descending altimeter, but the signal available assures performance at larger altitudes than previously expected.Publication Emission threshold for Cerenkov radiation(Monterey, CA; Naval Postgraduate School, 1985) Neighbours, John R.; Buskirk, Fred R.; Maruyama, Xavier K.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Naval Postgraduate School (U.S.); PhysicsPublication Improved Efficiency and Power Density for Thermoacoustic Coolers(Monterey, California. Naval Postgraduate School, 1996-06-11) Hofler, Thomas J.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); PhysicsWork continues on building a thermoacoustic heat driven cooler having no moving parts, with cooling power in the 0.5 to 1.0 kW range. Previous work dealt with numerical modeling of a new engine topology used in the above engine and various work on improved heat exchangers. Recently, morn modeling suggests that cooling powers in the range of 35 kW (10 ton) may be possible with an engine having a longest dimension of 4 ft. and that efficiency improves significantly with size. Also, we have solved some fabrication problems with our high temperature nickel heat exchangers. The major work this year has been on the high temperature thermoacoustic stack structure. A common Stirling engine regenerator structure consisting of stacked disks cut from stainless steel wire mesh was tested in an apparatus previously used for high amplitude heat exchanger measurements. Stacks are very easy to construct in this fashion and longitudinal thermal conduction is greatly reduced. Results show that amplitude performance is very good and within 10% of the usual spiral roll structures. More impressively, the efficiency of the mesh stack is as much as 30% higher than for spiral rolls stacks. We are also conducting measurements on pure carbon random structures that could be used at extremely high temperatures.Publication Modification, testing, and calibration of infrared search and target designator hardware received from NSWC(Monterey, California. Naval Postgraduate School, 1989-05) Crittenden, Eugene Casson; Cooper, Alfred William Madison; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Physics