Receptivity of Boundary Layer over a Blunt Wedge due to Freestream Pulse Disturbances at Mach 6

Direct numerical simulation (DNS) of a hypersonic compressible flow over a blunt wedge with fast acoustic disturbances in freestream is performed. The receptivity characteristics of boundary layer to freestream pulse acoustic disturbances are numerically investigated at Mach 6, and the frequency effects of freestream pulse wave on boundary layer receptivity are discussed. Results show that there are several main disturbance mode clusters in boundary layer under acoustic pulse wave, and the number of main disturbance clusters decreases along the streamwise. As disturbance wave propagates from upstream to downstream direction, the component of the modes below fundamental frequency decreases, and the component of the modes above second harmonic components increases quickly in general. There are competition and disturbance energy transfer between different boundary layer modes. The nose boundary layer is dominated by the nearby mode of fundamental frequency. The number of the main disturbance mode clusters decreases as the freestream disturbance frequency increases. The frequency range with larger growth narrows along the streamwise. In general, the amplitudes of both fundamental mode and harmonics become larger with the decreasing of freestream disturbance frequency. High frequency freestream disturbance accelerates the decay of disturbance wave in downstream boundary layer.

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NONLINEAR TRANSPORT OF ELECTRONS UNDER A STRONG HIGH FREQUENCY ELECTRIC FIELD IN SEMICONDUCTORS

International Journal of Modern Physics B ◽

10.1142/s0217979292000530 ◽

1992 ◽

Vol 06 (07) ◽

pp. 1007-1036 ◽

Cited By ~ 3

Author(s):

W. Cai ◽

M. Lax

Keyword(s):

Electric Field ◽

High Frequency ◽

Second Harmonic ◽

Memory Function ◽

Harmonic Component ◽

Nonlinear Transport ◽

Field Limit ◽

High Frequency Electric Field ◽

Dc Electric Field ◽

Harmonic Components

The nonlinear transport of electrons in semiconductors is studied when a strong high frequency (HF) electric field is applied together with a direct current (dc) electric field. A set of equations is developed, from which the amplitude and phase of each harmonic component of the electron drift velocity and the electron temperature can be computed. In the weak HF field limit our approach reduces to the well-known memory function method. The DC conductivity decreases and definitely becomes negative with increase of the first and second harmonic components of the applied HF field. Comparison is made with experiment.

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Stability characteristic of hypersonic flow over a blunt wedge under freestream pulse wave

Open Physics ◽

10.2478/s11534-014-0421-7 ◽

2014 ◽

Vol 12 (1) ◽

Cited By ~ 2

Author(s):

Xiaojun Tang ◽

Hongqing Lv ◽

Xiangnan Meng ◽

Zhenqing Wang ◽

Qin Lv

Keyword(s):

Boundary Layer ◽

Wall Temperature ◽

Fundamental Mode ◽

Pulse Wave ◽

Continuous Wave ◽

Second Harmonic ◽

Dominant Mode ◽

Stability Characteristic ◽

Hypersonic Boundary Layer ◽

The Stability

AbstractTo investigate the stability characteristic of hypersonic flow under the action of a freestream pulse wave, a high-order finite difference method was employed to do direction numerical simulation (DNS) of hypersonic unsteady flow over an 8° half-wedge-angle blunt wedge with freestream slow acoustic wave. The evolution of disturbance wave modes in the boundary layer under a pulse wave and a continuous wave are compared, and the wall temperature effect on the hypersonic boundary layer stability for a pulse wave disturbance is discussed. Results show that, both for a pulse wave and a continuous wave in freestream, the disturbance waves inside the nose boundary layer are mainly a fundamental mode; the Fourier amplitude of pressure disturbance mode in the boundary layer for a pulse wave is far less than that for a continuous wave, and the band frequency of the former is wider than that of the latter. All disturbance modes decay rapidly along the streamwise in the nose boundary layer. In the non-nose boundary layer, the dominant mode is transferred from fundamental mode into second harmonic. The transformation of dominant mode for a pulse wave appears much earlier than that for a continuous wave. Different frequency disturbance modes present different changes along streamline in the boundary layer, and the frequency band narrows around the second harmonic mode along the streamwise. Keen competition and the transformation of energy exist among different modes in the boundary layer. Wall temperature modifies the stability characteristic of the hypersonic boundary layer, which presents little effect on the development of fundamental modes and cooling wall could accelerates the growth of the high frequency mode as well as the dominant mode transformation.

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A new method of fluxgate signal extraction

Information extraction and processing ◽

10.15407/vidbir2017.45.083 ◽

2017 ◽

Vol 2017 (45) ◽

pp. 83-89

Author(s):

A.A. Marusenkov ◽

Keyword(s):

High Frequency ◽

Second Harmonic ◽

Excitation Frequency ◽

Low Noise ◽

Measuring System ◽

Signal Extraction ◽

Fluxgate Magnetometer ◽

New Approach ◽

Average Value ◽

The Time Domain

Using dedicated high-frequency measuring system the distribution of the Barkhausen jumps intensity along a reversal magnetization cycle was investigated for low noise fluxgate sensors of various core shapes. It is shown that Barkhausen (reversal magnetization) noise intensity is strongly inhomogeneous during an excitation cycle. In the traditional second harmonic fluxgate magnetometers the signals are extracted in the frequency domain, as a result, some average value of reversal magnetization noises is contributed to the output signals. In order to fit better the noise shape and minimize its transfer to the magnetometer output the new approach for demodulating signals of these sensors is proposed. The new demodulating method is based on information extraction in the time domain taking into account the statistical properties of cyclic reversal magnetization noises. This approach yields considerable reduction of the fluxgate magnetometer noise in comparison with demodulation of the signal filtered at the second harmonic of the excitation frequency.

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Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

Industrial laboratory Diagnostics of materials ◽

10.26896/1028-6861-2019-85-1-i-64-71 ◽

2019 ◽

Vol 85 (1(I)) ◽

pp. 64-71 ◽

Cited By ~ 1

Author(s):

M. M. Gadenin

Keyword(s):

High Frequency ◽

Experimental Studies ◽

Low Frequency ◽

Reduction Factor ◽

Single Frequency ◽

Cyclic Loads ◽

Small Ratio ◽

Harmonic Components ◽

Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

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Effects of Laryngeal Topical Anesthesia on Voice Fundamental Frequency Perturbation

Journal of Speech Language and Hearing Research ◽

10.1044/jshr.2302.274 ◽

1980 ◽

Vol 23 (2) ◽

pp. 274-283 ◽

Cited By ~ 19

Author(s):

David Sorensen ◽

Yoshiyuki Horii ◽

Rebecca Leonard

Keyword(s):

Fundamental Frequency ◽

High Frequency ◽

Frequency Control ◽

Topical Anesthesia ◽

Proprioceptive Feedback ◽

Adult Males ◽

Voice Fundamental Frequency

Fundamental frequency perturbation (jitter) during sustained vowel phonations of speakers under topical anesthesia of the larynx was investigated for five adult males. The results showed that the average jitter was significantly greater under the anesthesia than normal conditions, and that the jitter difference between the two conditions was more prominent at high frequency phonations. Implications of these data for tactile and proprioceptive feedback in phonatory frequency control are discussed.

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The appearance of boundary layers and drift flows due to high-frequency surface waves

Journal of Fluid Mechanics ◽

10.1017/jfm.2012.293 ◽

2012 ◽

Vol 707 ◽

pp. 482-495 ◽

Cited By ~ 24

Author(s):

Ofer Manor ◽

Leslie Y. Yeo ◽

James R. Friend

Keyword(s):

Boundary Layer ◽

Surface Waves ◽

High Frequency ◽

Slip Boundary Condition ◽

Inertial Effects ◽

Velocity Amplitude ◽

Slip Boundary ◽

Long Period ◽

Bulk Waves ◽

Schlichting Streaming

AbstractThe classical Schlichting boundary layer theory is extended to account for the excitation of generalized surface waves in the frequency and velocity amplitude range commonly used in microfluidic applications, including Rayleigh and Sezawa surface waves and Lamb, flexural and surface-skimming bulk waves. These waves possess longitudinal and transverse displacements of similar magnitude along the boundary, often spatiotemporally out of phase, giving rise to a periodic flow shown to consist of a superposition of classical Schlichting streaming and uniaxial flow that have no net influence on the flow over a long period of time. Correcting the velocity field for weak but significant inertial effects results in a non-vanishing steady component, a drift flow, itself sensitive to both the amplitude and phase (prograde or retrograde) of the surface acoustic wave propagating along the boundary. We validate the proposed theory with experimental observations of colloidal pattern assembly in microchannels filled with dilute particle suspensions to show the complexity of the boundary layer, and suggest an asymptotic slip boundary condition for bulk flow in microfluidic applications that are actuated by surface waves.

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Skin friction and surface temperature of an insulated flat plate fixed in a fluctuating stream

Journal of Fluid Mechanics ◽

10.1017/s0022112071000466 ◽

1971 ◽

Vol 46 (1) ◽

pp. 165-175 ◽

Cited By ~ 3

Author(s):

Hiroshi Ishigaki

Keyword(s):

Boundary Layer ◽

Surface Temperature ◽

Flat Plate ◽

Skin Friction ◽

High Frequency ◽

Energy Equation ◽

Oscillation Amplitude ◽

Flow Oscillation ◽

Velocity Amplitude ◽

The Mean

The time-mean skin friction of the laminar boundary layer on a flat plate which is fixed at zero incidence in a fluctuating stream is investigated analytically. Flow oscillation amplitude outside the boundary layer is assumed constant along the surface. First, the small velocity-amplitude case is treated, and approximate formulae are obtained in the extreme cases when the frequency is low and high. Next, the finite velocity-amplitude case is treated under the condition of high frequency, and it is found that the formula obtained for the small-amplitude and high-frequency case is also valid. These results show that the increase of the mean skin friction reduces with frequency and is ultimately inversely proportional to the square of frequency.The corresponding energy equation is also studied simultaneously under the condition of zero heat transfer between the fluid and the surface. It is confirmed that the time-mean surface temperature increases with frequency and tends to be proportional to the square root of frequency. Moreover, it is shown that the timemean recovery factor can be several times as large as that without flow oscillation.

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Pitch related to spectral edges of broadband signals

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1992.0071 ◽

1992 ◽

Vol 336 (1278) ◽

pp. 375-382 ◽

Cited By ~ 27

Keyword(s):

Fundamental Frequency ◽

Basilar Membrane ◽

Comparison Tone ◽

Harmonic Signals ◽

Wide Range ◽

Spectral Components ◽

Neuronal Processes ◽

Low Pass ◽

Harmonic Components ◽

Hearing System

A complex tone often evokes a pitch sensation associated with its extreme spectral components, besides the holistic pitch associated with its fundamental frequency. We studied the edge pitch created at the upper spectral edge of complexes with a low-pass spectrum by asking subjects to adjust the frequency of a sinusoidal comparison tone to the perceived pitch. Measurements were performed for different values of the fundamental frequency and of the upper frequency of the complex as well as for three different phase relations of the harmonic components. For a wide range of these parameters the subjects could adjust the comparison tone with a high accuracy, measured as the standard deviation of repeated adjustments, to a frequency close to the nominal edge frequency. The detailed dependence of the matching accuracy on temporal parameters of the harmonic complexes suggests that the perception of the edge pitch in harmonic signals is related to the temporal resolution of the hearing system. This resolution depends primarily on the time constants of basilar-membrane filters and on additional limitations due to neuronal processes.

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