• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6B
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• pp.571-578
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• 2010

Manning's roughness coefficients were reevaluated for the computation of river flow of the Han River, the Nakdong River and the Geum River. The roughness coefficients were estimated by two methods. One is based on the assumption that roughness is primarily a function of grain diameter and the other is based on the findings that roughness may vary significantly with the flow discharge. The roughness coefficients adopted in each river improvement master plan have been compared with those obtained using the FLDWAV in this study, and their applicabilities have been reviewed, using the FLDWAV and HEC-RAS models. The design flood water levels computed by the abovementioned models with the roughness coefficients proposed in this study have shown good agreement with the measurements of time variation. The roughness coefficients computed using the FLDWAV model showed nearly no close correlation with the various hydraulic characteristic factors, such as grain size and river depth, etc.. Finally the design flood water levels and levee safety about the downstream part from the Paldang Dam of the Han River has been reviewed using HEC-2 model with roughness coefficients of this study and the results indicated that some parts of the existing levees were short of safety.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1306-1310
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• 2009

The roughness coefficients were estimated by the Manning's equation for the measured stage and flow velocity of Bocheong stream basin in Kum river. The relationships between the estimated roughness coefficients and the geomorphologic factors were formulated by the linear, logarithmic, exponential and power type function, thereafter correlation equations were presented. The correlation analysis was performed between the measured stream length and the basin area of Bocheong stream basin by the linear, logarithmic, exponential and power type function, and correlation equation for the stream length was given. The roughness coefficient has strong correlationship with stream slope, but low correlation coefficients with stream length and basin area. For the correlationship with the roughness coefficients and the stream slope, the logarithmic type function has the smallest correlation coefficient, on the other hand, the exponential type function has the largest correlation coefficient. For the relationship between the stream length and the basin area, the correlation coefficient of the logarithmic type function shows the smallest value, linear type function shows the largest value.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6B
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• pp.345-354
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• 2012

The main objective of this study is evaluating experimentally roughness coefficients of the Korean riparian vegetations based on the n-VR analysis to suggest the practical guideline for Manning's roughness coefficients for the channel design. Hydraulic experiments were conducted for Phragmites japonica Steud., Miscanthus sacchariflorus (Maxim.) Benth., and Phragmites communis Trin. under both submerged and un-submerged conditions, and the n-VR relationships are developed for each grass. Three vegetations tested in this study can be considered as same group showing similar roughness characteristics, though these grasses are strongly affected by vegetation stiffness. Vegetation roughness are also affected by the growth state of plants according to experimental results of Phragmites communis Trin.

• Journal of Sasang Constitutional Medicine
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• v.22 no.4
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• pp.20-29
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• 2010

1. Objectives Our goal is to observe the feasibility of constitution discrimination from computing quantitative roughness index from dynamic friction coefficients and their gradients with the measurement device of skin friction with 3-Axis load cell sensor. 2. Methods In the traditional Korean medicine, skin diagnosis is one of the examination methods to discriminate Sasang constitution since it was known that Tae-eumin has rough skin, and Soyangin has smooth one. It is based on the skin roughness on the back of one's hand for the discrimination. The measurement device of skin friction with 3-axis load cell sensor has been developed in order to provide quantitative skin roughness through dynamic friction coefficients. The effective interval of the coefficients is obtained from the automatic sampling algorithm to use their curvature and slope. Then, Fisher's discriminant function of them makes the discrimination. 3. Results The success rate of extracting the effective interval was about 90% and the discriminant accuracy between Tae-eumin and Soyangin was 70% and 68% for men and women, respectively. The entire methods showed the possibility to distinguish between Tae-eumin and Soyangin by using stochastic properties of roughness index, which can make the entire system to include the measurement, the computation of the roughness index and the discrimination of constitution automatical. 4. Conclusions The measurement device, the automatic sampling algorithm of dynamic friction coefficients and the constitution discrimination algorithm were developed, respectively, and their combination can become the serial and automatic procedure for quantitative and objective skin diagnosis, which mimics the movement of the Oriental medical doctors' skin diagnosis. It can be applied to healthcare as well as the diagnosis of constitution in a u-Health system soon.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.91-97
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• 2013

The input parameters of scattering models for computing the backscattering coefficients of earth terrains are mainly soil moisture and surface roughness. The backscattering coefficients of soil surfaces are more sensitive to surface roughness than soil moisture. In this study, we propose a precise measurement method for roughness parameters and analyze measurement errors. We measured surface roughness using a pin-board profiler(1 m, 0.5 cm interval) and a laser profiler(1 m, 0.25 cm interval). The measurement differences between two profilers in an average sense are 0.097 cm for root-mean-square (RMS) height and 1.828 cm for correlation length. The analysis of the correlation functions and relative errors shows that the laser measurements are more stable than the pin-board measurements. The differences of the calculated backscattering coefficients using a surface scattering model between pin-board and laser profiler measurements are less than 1 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1181-1188
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• 2006

The radar backscattering coefficients of soil surfaces with various roughness conditions are computed at first in this paper. The roughness parameters for various surface-profile lengths are also obtained. Then, the relationship between the radar backscattering coefficients and the profile length is studied. It was shown that the effect of the profile length is negligible on the backscattering coefficient, even though the roughness parameters vary a lot with the length of the surface profile.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.113-121
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• 2012

The study was carried out to investigate the dimension of irrigation canal, and measure the water flow of those diverted from Kimje main canal in Dongjin irrigation area. The rating curves indicating the relationships between water level and discharge of the lateral canals were induced using the measured data with high regression coefficients of 0.957~0.999 at inlet points and 0.932~0.998 at end points, respectively. And Manning's roughness coefficients were estimated as the ranged from 0.015 to 0.074 at inlet points and 0.056 to 0.089 at end points with rectangular type of concrete open irrigation canals, the Manning's roughness coefficients of the end points were less than those values of the end points, which may be considered as the deposition of the bottom sediments.

• Proceedings of the KSRS Conference
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• v.1
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• pp.520-523
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• 2006

Whereas it is well known that the surface roughness parameters, the RMS height and the correlation length, of a natural soil surface are underestimated with a short surface profile, it is not clear how much the underestimated surface parameters affect the backscattering coefficients of the surface for various incidence angles and polarizations. The backscattering coefficients of simulated and measured surface profiles are computed using the integral equation method (IEM) and analyzed in this paper to answer this question. It is shown that the RMS error of the backscattering coefficients between 5-m- and 1-m-long measured surface profiles is 1.7 dB for vv-polarization and 0.5 dB for hh-polarization at a medium range of incidence angle ($15^{\circ}{\leq}{\theta}{\leq}70^{\circ}$), while the surface roughness parameters are significantly reduced; from 2.4 cm to 1.5 cm for the RMS height s and from 35.1 cm to 10.0 cm for the autocorrelation length l. This result is verified with numerous simulations with various roughness conditions and various wavelengths.

• Water for future
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• v.28 no.6
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• pp.133-146
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• 1995

Manning's roughness coefficient for the Han River (from Paldang dam to Indo Bridge) is estimated by one-dimensional unsteady flow model, NETWORK. The entire river is divided into two regions, one region of Paldang dam to Kwangjang, and another region of Jamsu Bridge to Indo Bridge, and changes of the roughness coefficient according to changes in discharge are estimated using data of the past flood events. Estimated roughness coefficients are compared with previous results. Finally, the stage variation according to the variation of channel roughness is presented.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.3
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• pp.301-312
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• 1983

Experimental results for the variation of the flow characteristics and heat transfer coefficients in the entrance region of concentric annular pipe with artificial roughness are compared with the theoretical results by numerical analysis. In the experiments, velocity profiles, pressure gradients and heat transfer coefficients were measured with variation of the Reynolds number for the constant ratio of pitch to height at the hydrodynamic entry region. Wall temperature of inner heated pipe with constant heat flux was measured at thermal entry region after the hydrodynamically fully developed region of flow. Experimental data agree well with numerical predictions. Both results show that turbulent flow of annular pipe with artificial roughness is fully developed thermally much faster than that of smooth pipe. Nusselt number of annular pipe with roughness is much higher than that of smooth pipe. However the ratios of Nusselt number of annular pipe with artificial roughness to that of smooth pipe does not vary with Reynolds number.