Alluvial Flow Resistance—Engelund Sediment Waveform

The effect of vegetation in hydraulic computations can be significant. This effect is important for flood computations. Today, the necessary terrain information for flood computations is obtained by airborne laser scanning techniques. The quality and density of the airborne laser scanning information allows for more extensive use of these data in flow computations. In this paper, known methods are improved and combined into a new simple and objective procedure to estimate the hydraulic resistance of vegetation on the flow in the field. State-of-the-art airborne laser scanner information is explored to estimate the vegetation density. The laser scanning information provides the base for the calculation of the vegetation density parameter ωp using the Beer–Lambert law. In a second step, the vegetation density is employed in a flow model to appropriately account for vegetation resistance. The use of this vegetation parameter is superior to the common method of accounting for the vegetation resistance in the bed resistance parameter for bed roughness. The proposed procedure utilizes newly available information and is demonstrated in an example. The obtained values fit very well with the values obtained in the literature. Moreover, the obtained information is very detailed. In the results, the effect of vegetation is estimated objectively without the assignment of typical values. Moreover, a more structured flow field is computed with the flood around denser vegetation, such as groups of bushes. A further thorough study based on observed flow resistance is needed.

Download Full-text

A Test Method to Determine Air Flow Resistance of Exterior Membranes and Sheathings

Journal of Thermal Insulation ◽

10.1177/109719638600900304 ◽

1986 ◽

Vol 9 (3) ◽

pp. 224-235 ◽

Cited By ~ 8

Author(s):

M. Bomberg ◽

M.K. Kumaran

Keyword(s):

Flow Resistance ◽

Air Flow ◽

Test Method

Download Full-text

Evaluating the Effects of Sediment Transport on Pipe Flow Resistance

Water ◽

10.3390/w13152091 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2091

Author(s):

Vito Ferro ◽

Alessio Nicosia

Keyword(s):

Velocity Profile ◽

Pipe Flow ◽

Power Distribution ◽

Flow Resistance ◽

Unit Length ◽

Particle Diameter ◽

Self Similarity ◽

Sediment Size ◽

The Mean ◽

The Relationship

In this paper, the applicability of a theoretical flow resistance law to sediment-laden flow in pipes is tested. At first, the incomplete self-similarity (ISS) theory is applied to deduce the velocity profile and the corresponding flow resistance law. Then the available database of measurements carried out by clear water and sediment-laden flows with sediments having a quasi-uniform sediment size and three different values of the mean particle diameter Dm (0.88 mm, 0.41 mm and 0.30 mm) are used to calibrate the parameter of the power-velocity profile). The fitting of the measured local velocity to the power distribution demonstrates that (i) for clear flow the exponent δ) can be estimated by the equation of Castaing et al. and (ii) for the sediment-laden flows δ is related to the diameter Dm. A relationship for estimating the parameter Гv obtained by the power-velocity profile) and that Гf of the flow resistance law) is theoretically deduced. The relationship between the parameter Гv, the head loss per unit length and the pipe flow Froude number is also obtained by the available sediment-laden pipe flow data. Finally, the procedure to estimate the Darcy–Weisbach friction factor is tested by the available measurements.

Download Full-text

Effect of Subglottic Stenosis on Vocal Fold Vibration and Voice Production Using Fluid–Structure–Acoustics Interaction Simulation

Applied Sciences ◽

10.3390/app11031221 ◽

2021 ◽

Vol 11 (3) ◽

pp. 1221

Author(s):

Dariush Bodaghi ◽

Qian Xue ◽

Xudong Zheng ◽

Scott Thomson

Keyword(s):

Flow Rate ◽

Vocal Fold ◽

Flow Resistance ◽

Signal To Noise Ratio ◽

Area Ratio ◽

Subglottic Stenosis ◽

Fluid Structure ◽

Voice Production ◽

Vocal Fold Vibration ◽

Glottal Flow

An in-house 3D fluid–structure–acoustic interaction numerical solver was employed to investigate the effect of subglottic stenosis (SGS) on dynamics of glottal flow, vocal fold vibration and acoustics during voice production. The investigation focused on two SGS properties, including severity defined as the percentage of area reduction and location. The results show that SGS affects voice production only when its severity is beyond a threshold, which is at 75% for the glottal flow rate and acoustics, and at 90% for the vocal fold vibrations. Beyond the threshold, the flow rate, vocal fold vibration amplitude and vocal efficiency decrease rapidly with SGS severity, while the skewness quotient, vibration frequency, signal-to-noise ratio and vocal intensity decrease slightly, and the open quotient increases slightly. Changing the location of SGS shows no effect on the dynamics. Further analysis reveals that the effect of SGS on the dynamics is primarily due to its effect on the flow resistance in the entire airway, which is found to be related to the area ratio of glottis to SGS. Below the SGS severity of 75%, which corresponds to an area ratio of glottis to SGS of 0.1, changing the SGS severity only causes very small changes in the area ratio; therefore, its effect on the flow resistance and dynamics is very small. Beyond the SGS severity of 75%, increasing the SGS severity, leads to rapid increases of the area ratio, resulting in rapid changes in the flow resistance and dynamics.

Download Full-text