Civil Engineering Reports
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From 1947 to 1996, the Colorado State University Department of Civil Engineering issued reprints of engineering papers, bulletins, and documents as the series Civil Engineering Reports. University faculty and students authored most reports, and the department assigned report numbers in order of acquisition for each year. The series grew to more than 2,000 reports, of which nearly 1,300 are available in this digital collection.
Other CERs may be found in Mountain Scholar - Archives and Special Collections and in the Groundwater Data Collection.
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Browsing Civil Engineering Reports by Subject "Aerodynamics"
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Item Open Access Aerodynamics: a time dependent flow model for the inner region of a turbulent boundary layer(Colorado State University. Libraries, 1981-04) Chien, Ho-Chen, author; Sandborn, Virgil A., author; Department of Civil Engineering, Colorado State University, publisherResponse of the flow variables to external driving forces is non-linear for shear flows. For the turbulent boundary layer case, surface shear stress fluctuations of magnitude as great as the mean value are observed. For flow near the surface Prandtl's turbulent boundary layer approach of employing averaged Reynolds equation and a turbulence closure model is insufficient to account for surf ace shear fluctuations. A model which incorporates a discrete time dependent solution for the inner region of the turbulent boundary layer is proposed. The model requires stochastic averaging of the time dependent solution to account for the random aspect of the flow. The physical model for the flow near the surface is based on the bursting cycle observed in the inner region of a turbulent boundary layer. Localized pressure gradients created in the valleys of the large scale structures of the outer region of the flow are assumed to be the origin of the bursting process. This model treats the sweep motion as an impulsively started flow over a flat plate. An averaging technique is demonstrated to predict the important features of the surface shear stress. In order to confirm the time dependent model assumptions, measurements of the probability distribution and cross-correlation of the longitudinal turbulent velocity and the surface shear stress were evaluated. The sweep-scale, sweep-direction, and origin of the instability are determined from isocorrelation maps. The shape of the probability density distributions of the velocity near the surface and the surface shear stress are found to be similar. However, the velocity probability distribution changes rapidly with increasing distance from the surface. As implied by the time dependent model for the surface shear stress, the magnitude of the large surface shear stress would be substantially changed if the sweep motion could be modified. A series of thin, metal plates were employed to block the instability from reaching the surface. Results show that the mean value of surface shear and the large magnitude fluctuations of surface shear stress were reduced significantly. The variation in surface shear was found to be extremely sensitive to slight angle of attacks of the plates.Item Open Access Aerodynamics: control of surface shear stress fluctuations in turbulent boundary layers(Colorado State University. Libraries, 1981) Sandborn, Virgil A., author; Department of Civil Engineering, Colorado State University, publisherItem Open Access Complete development of the turbulent distribution of velocity in smooth ducts(Colorado State University. Libraries, 1956) Reichardt, H., author; Shweizer, Herbert H., author; VDI-Verlag, G. M. B. H., publisherItem Open Access Cone frustums in a shear layer: technical report(Colorado State University. Libraries, 1970) Symes, Craig R., author; Meroney, Robert N., author; Fluid Dynamics and Diffusion Laboratory, College of Engineering, Colorado State University, publisherItem Open Access Development of a miniature air velocity indicator: experimental study to determine sensitivity of new designs(Colorado State University. Libraries, 1954-07) Cermak, Jack E., author; Koloseus, Herman J., authorItem Open Access Flow separation in time varying flow(Colorado State University. Libraries, 1969-12) Sandborn, Virgil A., author; Chou, Fang-Kuo, author; Fluid Dynamics and Diffusion Laboratory, College of Engineering, Colorado State University, publisherAn exact solution of time varying pipe flow with a fluctuating velocity superimposed on the mean flow is analyzed. The velocity profiles, together with the profile parameters at separation, are computed from a computer program. The results are compared with the model for relaxed (steady) and unrelaxed (unsteady) separation criteria proposed by V. A. Sandborn and S. J. Kline. For very low frequencies, the correlation curves appear to have a reasonable agreement with the proposed relaxed separation criterion. For high frequencies, the correlation curves have been found to fall approximately on the unrelaxed separation criterion. This result demonstrates further that adjustment time is an important factor for separation to be relaxed or unrelaxed, a new concept proposed by Sandborn. In addition, J. T. Stuart's solution for the flow along an infinite flat plate with normal suction and periodic external velocity is further analyzed. The results again prove to agree with the proposed new concept.Item Open Access Fundamental study of a submerged and non-submerged three dimensional jet impinging upon a normal plane(Colorado State University. Libraries, 1963) Tsuei, Yeong-Ging, author; Chao, Junn-Ling, author; Baldwin, Lionel V., author; Colorado State University, Engineering Research Center, publisherPart I, Axisymmetric boundary-layer of a jet impinging on a smooth plate: The flow characteristics of a radial wall jet formed by the normal impingement of an air jet on a smooth fiat plate have been studied. The mean velocity and the turbulence statistics for different orifice velocities and diameters were measured with a pitot tube and a hot-wire anemometer. Most of the measurements were made at ten vertical stations spaced at 6 in. intervals along a radius. The first station was twelve inches from the stagnation point. A particular form for the turbulent shear stress is proposed. Using the incompressible boundary-layer approximations and a similarity assumption, the momentum and continuity equations were used to derive expressions in the form of a n exponential decay for the peak radial velocity and a linear growth for the boundary layer thickness with respect to the radial distance from the center. The measured profiles of velocity and turbulent intensities were found to be approximately similar; thus, approximate universal functions were obtained by expressing U/(U sub m) ,√(U12)(U sub m), √(V12)/(U sub m) and √(W12)/(U sub m) (the relative velocity and turbulent intensities respectively) in terms of a non-dimensional vertical coordinate L = ʓ/(δ sub 0.5). The characteristic length (δ sub 0.5) was chosen as the height where U/(U sub m) = 0.5. The mean velocity profile of the inner boundary-layer does not follow the pipe wall law and only a limited region can be approximated by the logarithmic form. This is attributed to the effects of the highly turbulent flow within the outer layer of the wall jet which produces disturbances penetrating deeply into the inner boundary-layer. Consequently, a higher wall shear stress results in this wall jet flow than in ordinary two- dimensional boundary-layer flow. The wall s hear stress was found to be approximately proportional to the invers e square of the radial distance.Item Open Access Prediction of the turbulent boundary layer separation(Colorado State University. Libraries, 1973-07) Chou, Fang-Kuo, author; Sandborn, Virgil A., author; Fluid Dynamics and Diffusion Laboratory, College of Engineering, Colorado State University, publisherA method for the prediction of the location of turbulent boundary layer separation is developed. The method is based on the inner and outer velocity distributions technique developed by Stratford, together with a separation criterion, which applies directly to the separation position. For the inner region, the model employs the empirical one-parameter boundary layer separation profiles proposed by Sandborn and Kline. For the outer region, the equivalent velocity distribution for the flow on a flat plate has been used. The resulting formula for predicting the separation position is a simple non-linear algebraic equation. The method is tested by comparing with several well-documented separation measurements. The results show a good agreement in the prediction of the position of turbulent separation. The calculated pressure rise to separation is also in good agreement with experimental results. An experimental study for a turbulent boundary layer up to and through the separation region has been made to further demonstrate the present method. The measurements were taken along the test wall of a two dimensional diffuser. Mean quantities, turbulent intensities, and the wall shear stresses were measured. The velocity profile integral parameters were evaluated from the measured data. The results are also compared with the separation model suggested by Sandborn and Kline. At the start of the separation region, the velocity profile correlation falls approximately on the unrelaxed separation correlation curve given by Sandborn and Kline. The velocity profiles in the separation region are well represented by the two-parameter separation profiles suggested by Sandborn.