Unsteady plane flow past curved obstacles with infinite wakes

1955 ◽  
Vol 229 (1177) ◽  
pp. 152-180 ◽  
Keyword(s):  
Unsteady Flow ◽  
Classical Theory ◽  
Steady Motion ◽  
Uniform Motion ◽  
Plane Flow ◽  
Flow Past ◽  
Long Duration ◽  
Infinite Extent ◽  
The Mean ◽  
Special Case

A theory of unsteady flow about obstacles behind which are wakes or cavities of infinite extent is developed for the case when the velocities and displacements of the unsteady perturbations about the mean steady motion are small. Unsteady Helmholtz flows (constant wake pressure) receive detailed attention both for general non-uniform motion and for the special case of harmonic motions of long duration. A number of possible applications of the theory to aerodynamic problems are indicated, the most important being the flutter of a stalled aerofoil. The classical theory of unsteady aerofoik motion is shown to be a special case of the theory given in this paper.

The Estimation of Discharge in an Experimental Open Channel

2014 ◽  
Vol 905 ◽  
pp. 369-373
Author(s):  
Choo Tai Ho ◽  
Yoon Hyeon Cheol ◽  
Yun Gwan Seon ◽  
Noh Hyun Suk ◽  
Bae Chang Yeon
Keyword(s):  
Unsteady Flow ◽  
River Discharge ◽  
Open Channel ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Velocity Equation ◽  
The Mean ◽  
Loop Form

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

Computation of unsteady flow past a cylinder instantaneously set in motion

1977 ◽  
Vol 17 (5) ◽  
pp. 671-677
Author(s):  
V. I. Kravchenko ◽  
Yu. D. Shevelev ◽  
V. V. Shchennikov
Keyword(s):  
Unsteady Flow ◽  
Flow Past ◽  
Flow Past A Cylinder

The behaviour of supersonic flow past a body of revolution, far from the axis

1950 ◽  
Vol 201 (1064) ◽  
pp. 89-109 ◽  
Keyword(s):  
Supersonic Flow ◽  
General Theory ◽  
Body Of Revolution ◽  
Flow Past ◽  
Physical Importance ◽  
Special Case ◽  
Pointed Body ◽  
Asymptotic Forms

A theory is developed of the supersonic flow past a body of revolution at large distances from the axis, where a linearized approximation is valueless owing to the divergence of the characteristics at infinity. It is used to find the asymptotic forms of the equations of the shocks which are formed from the neighbourhoods of the nose and tail. In the special case of a slender pointed body, the general theory at large distances is used to modify the linearized approximation to give a theory which is uniformly valid at all distances from the axis. The results which are of physical importance are summarized in the conclusion (§ 9) and compared with the results of experimental observations.

scholarly journals The Steady Profile of an Axisymmetric Ice Sheet

1981 ◽  
Vol 27 (95) ◽  
pp. 25-37 ◽  
Author(s):  
I. R. Johnson
Keyword(s):  
Aspect Ratio ◽  
Power Law ◽  
Viscous Incompressible Fluid ◽  
Ice Sheet ◽  
Plane Flow ◽  
The Third ◽  
Basal Sliding ◽  
Steady Plane ◽  
Third Dimension ◽  
Special Case

AbstractSteady plane flow under gravity of an axisymmetric ice sheet resting on a horizontal rigid bed, subject to surface accumulation and ablation, basal drainage, and basal sliding is treated according to a power law between shear traction and velocity. The surface accumulation is taken to depend on height, and the drainage and sliding coefficient also depend on the height of overlying ice. The ice is described as a general non-linearly viscous incompressible fluid, and temperature variation through the ice sheet is neglected. Illustrations are presented for Glen’s power law (including the special case of a Newtonian fluid), and the polynomial law of Colbeck and Evans. The analysis follows that of Morland and Johnson (1980) where the analogous problem for an ice sheet deforming under plane flow was considered. Comparisons are made between the two models and it is found that the effect of the third dimension is to reduce (or leave unchanged) the aspect ratio for the cases considered, although no general formula can be obtained. This reduction is seen to depend on both the surface accumulation and the sliding law.

scholarly journals ANALISIS DESKRIPTIF BERBASIS MODEL MENTAL FISIKA TERHADAP PEMAHAMAN KOGNITIF MAHASISWA PADA KONSEP KINEMATIKA PARTIKEL DAN GERAK PARABOLA

2020 ◽  
Vol 3 (3) ◽  
pp. 255-260
Author(s):  
Nyoman Rohadi ◽  
Iwan Setiawan
Keyword(s):  
Physics Education ◽  
Mental Model ◽  
Uniform Motion ◽  
Study Program ◽  
First Semester ◽  
Education Study ◽  
The Mean ◽  
Motion Problems ◽  
Physics Problems

ABSTRAK Artikel ini menguraikan hasil analisis deskriptif berbasis model mental fisika terhadap pemahaman kognitif mahasiswa semester pertama tahun ajaran 2019/2020 prodi pendidikan fisika JPMIPA FKIP UNIB Universitas Bengkulu pada konsep kinematika partikel dan gerak parabola. Data yang dianalisis diperoleh dari hasil pretest, lembar kerja mahasiswa (LKM),  dan data hasil posttest dari mahasiswa yang berjumlah 28 orang mengikuti kuliah fisika dasar 1. Skor rata-rata data hasil Pretest adalah  44,64 pada rentang nilai yang cukup lebar yaitu 30-80. Skor rata-rata pada data hasil Posttest adalah 71,42 dengan rentang 50-100. Skor rata-rata pada posttest mengalami peningkatan  sebesar 26,78 atau 60% terhadap skor rerata Pretest. Hasil analisis deskriptif pada data hasil pretest dan LKM menunjukkan  rendahnya penguasaan mahasiswa dalam memahami soal-soal bentuk diagram gambar fisika dan grafik fisika. Tetapi mahasiswa tidak mengalami kesulitan dalam menerapkan rumus-rumus untuk  menjawab soal-soal konsep GLB. meskipun ada sejumlah mahasiswa salah menentukan besarnya percepatan pada soal GLBB. Dari analisis pada posttest menunjukkan adanya peningkatan kompetensi kognitif pada mahasiswa.  Mahasiswa telah mampu menerapkan model mental fisika dalam memahami dan memecahkan soal-soal berbentuk konseptual, diagram, grafik, dan penerapan rumus fisika  pada materi kinematika partikel, dan konsep gerak parabola.  Kata kunci: model mental, kompetensi kognitif, kinematika partikel dan gerak parabola ABSTRACT This article portrays a deskriptif analysis results based on physics mental model toward cognitif reasoning of the first semester in the year of study 2019/2020 students in physics education study program of  the JPMIPA FKIP Bengkulu University on the concepts of kinematics particle and parabolic motion. The analized data were a pretestt, students work sheets (SWS) and posttest data Of 28 students who participated in basics physics 1 class. The mean score of the pretestt data was 44,64 in a range score  of 30.00-80.00. The mean score of the posttest data was 71,42 in a range score of 50.00-100.00. The mean score of posttest increased about 60% compare with the mean score of pretestt.  The deskriptif analysis on the pretestt data and the SWS data indicated that a low kognitif competency among the students in understanding physics diagram and solving physics graphs related problems. But no student faund any dificulty in using physics equations on solving the uniform motion problems. Eventhough some students failed in solving the amount of  acceleration related problems. The analysed results of the posttest data indicated an improvement on students kognitif competency. Most of the students could apply the physics mental model on solving the conceptual, diagram, graph, and matematics related physics problems. Keywords: mental model, kognitif competency, arithmatics particle, and parabolics motion.

Flow Unsteadiness and Stability Characteristics of Low-Re Flow Past an Inclined Triangular Cylinder

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Wei Zhang ◽  
Hui Yang ◽  
Hua-Shu Dou ◽  
Zuchao Zhu
Keyword(s):  
Growth Rate ◽  
Sensitivity Analysis ◽  
Unsteady Flow ◽  
Maximum Velocity ◽  
Flow Patterns ◽  
Wake Flow ◽  
Near Wake ◽  
Flow Unsteadiness ◽  
Flow Past ◽  
Far Wake

The present study investigates the two-dimensional flow past an inclined triangular cylinder at Re = 100. Numerical simulation is performed to explore the effect of cylinder inclination on the aerodynamic quantities, unsteady flow patterns, time-averaged flow characteristics, and flow unsteadiness. We also provide the first global linear stability analysis and sensitivity analysis on the targeted physical problem for the potential application of flow control. The objective of this work is to quantitatively identify the effect of cylinder inclination on the characteristic quantities and unsteady flow patterns, with emphasis on the flow unsteadiness and instability. Numerical results reveal that the flow unsteadiness is generally more pronounced for the base-facing-like cylinders (α → 60 deg) where separation occurs at the front corners. The inclined cylinder reduces the velocity deficiency in the near-wake, and the reduction in far-wake is the most notable for the α = 30 deg cylinder. The transverse distributions of several quantities are shifted toward the negative y-direction, such as the maximum velocity deficiency and maximum/minimum velocity fluctuation. Finally, the global stability and sensitivity analysis show that the spatial structures of perturbed velocities are quite similar for α ≤ 30 deg and the temporal growth rate of perturbation is sensitive to the near-wake flow, while for α ≥ 40 deg there are remarkable transverse expansion and streamwise elongation of the perturbed velocities, and the growth rate is sensitive to the far-wake flow.

Unsteady flow past a flat plate with suction

1975 ◽  
Vol 81 (5) ◽  
pp. 215-219 ◽  
Author(s):  
G. N. Purohit ◽  
M. C. Goyal
Keyword(s):  
Unsteady Flow ◽  
Flat Plate ◽  
Flow Past

Two patterns of daily hypoxic exposure and their effects on measures of chemosensitivity in humans

2007 ◽  
Vol 103 (6) ◽  
pp. 1973-1978 ◽  
Author(s):  
Michael S. Koehle ◽  
A. William Sheel ◽  
William K. Milsom ◽  
Donald C. McKenzie
Keyword(s):  
Oxygen Saturation ◽  
Intermittent Hypoxia ◽  
Ventilatory Response ◽  
Arterial Oxygen Saturation ◽  
Arterial Oxygen ◽  
Hypoxic Exposure ◽  
Hypoxic Ventilatory Response ◽  
The Third ◽  
Long Duration ◽  
The Mean

The purpose of this study was to compare chemoresponses following two different intermittent hypoxia (IH) protocols in humans. Ten men underwent two 7-day courses of poikilocapnic IH. The long-duration IH (LDIH) protocol consisted of daily 60-min exposures to normobaric 12% O2. The short-duration IH (SDIH) protocol comprised twelve 5-min bouts of 12% O2, separated by 5-min bouts of room air, daily. Isocapnic hypoxic ventilatory response (HVR) was measured daily during the protocol and 1 and 7 days following. Hypercapnic ventilatory response (HCVR) and CO2 threshold and sensitivity (by the modified Read rebreathing technique) were measured on days 1, 8, and 14. Following 7 days of IH, the mean HVR was significantly increased from 0.47 ± 0.07 and 0.47 ± 0.08 to 0.70 ± 0.06 and 0.79 ± 0.06 l·min−1·%SaO2−1 (LDIH and SDIH, respectively), where %SaO2 is percent arterial oxygen saturation. The increase in HVR reached a plateau after the third day. One week post-IH, HVR values were unchanged from baseline. HCVR increased from 3.0 ± 0.4 to 4.0 ± 0.5 l·min−1·mmHg−1. In both the hyperoxic and hypoxic modified Read rebreathing tests, the slope of the CO2/ventilation plot was unchanged by either intervention, but the CO2/ventilation curve shifted to the left following IH. There were no correlations between the changes in response to hypoxia and hypercapnia. There were no significant differences between the two IH protocols for any measures, indicating that comparable changes in chemoreflex control occur with either protocol. These results also suggest that the two methods of measuring CO2 response are not completely concordant and that the changes in CO2 control do not correlate with the increase in the HVR.

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