Crest Length Research Articles

Flow Characteristics of Triangular Plan Form Weir

Weirs are used for discharge measurement and flow diversion in the open channels. However, modified weirs such as plan form weirs, Labyrinth weir, oblique weir and piano key weir, etc. having larger crest length compared to normal weir having same lateral space assist in enhancing discharging capacity for a given upstream head, without creating much afflux. An experimental study was carried out to understand the effect of the geometry of a triangular plan form weir on discharge coefficient under free and submerged flow conditions. In this paper attempts are made to investigate working of triangular plan form weir of vertex angle 45° with three heights 10, 20 and 30 cm under free and submerged flow conditions. The discharge coefficients were calculated under free & submerged flow conditions and the results were compared with normal weirs as well. Further, triangular plan form weir is quite simple device/geometry and easy to install & quite useful for discharge measurement in open channels.

Prediction of discharge coefficient of triangular labyrinth weirs using Adaptive Neuro Fuzzy Inference System

In this paper, the discharge coefficient of triangular labyrinth weir was predicted using multi-layer perceptron (MLP) neural network and Adaptive Neuro Fuzzy Inference System (ANFIS). To this purpose, 223 related dataset were collected. The Gamma Test (GT) was carried out to obtain the most affective parameters on the discharge coefficient. The results of the GT indicated that the ratio of length of crest of weir to the main channel width Lw/Wmc, the ratio of length of one cycle to its width (Lc/Wc) and the ratio of total upstream head flow to the weir height H/P are the most important parameters. With regarding to the results of the GT, the structure of ANFIS model was designed. The results of ANFIS model with error indices including coefficient of determination value of 0.97 and root mean square error value of 0.03 was so suitable. Comparison the results of MLP with ANFIS model showed that both models has so suitable performance however the structure of ANFIS model is more optimal.

Morphological beak differences of loliginid squid, Uroteuthis chinensis and Uroteuthis edulis, in the northern South China Sea

The mitre squid (Uroteuthis chinensis) and the swordtip squid (U. edulis) are Indo-Pacific cephalopod species that are abundant in the western Pacific Ocean. They are currently exploited in the East and South China Seas and make up a significant portion of the Chinese neritic squid catch. Beaks, the feeding organs of squid, are important for individual size and biomass estimation because of their high resistance to degradation in predator stomachs and consistent dimensions. In this study, 104 U. chinensis and 143 U. edulis individuals were sampled from northern South China Sea with mantle length from 70 to 260 mm and 96 to 284 mm, respectively. The results indicated that morphological beak values were greater for U. edulis, compared to U. chinensis, for upper hood length (UHL), upper crest length (UCL), upper lateral wall length (ULWL), lower crest length (LCL), and lower lateral wall length (LLWL). According to principal component analysis, UHL/ML, UCL/ML, ULWL/ML, LCL/ML, LLWL/ML and LWL/ML could represent the characteristics of beaks for U. chinensis, while UHL/ML, UCL/ML, ULWL/ML, LHL/ML, LCL/ML and LLWL/ML could represent it for U. edulis. According to Akaike’s information criterion (AIC) values, a power function was the most suitable model for U. chinensis, while a linear function was the most suitable model for U. edulis. The beak variable-mantle length ratio (beak variable/mantle length) declined with the increasing of mantle length and declined sharply at the early stage of growth in both beaks and species. The ratio changed quickly after achieving the mantle length of 140 mm for U. chinensis, while the ratio changed quickly after 170 mm for U. edulis. Beaks in both species experienced sharper changes through maturity stage I to II than other maturity stages. This study gives us basic beak morphology information for U. chinensis and U. edulis in the East and South China Seas. Geometric morphological methods combined with dietary analysis should be used in the future.

Determining discharge coefficient of labyrinth and arced labyrinth weirs using support vector machine

Abstract A labyrinth weir is a linear weir folded in plan-view which increases the crest length and the flow rate for a given channel width and an upstream flow depth. The present study aimed at determining discharge coefficients of labyrinth and arced labyrinth weirs using support vector machine (SVM)-based models. A total of 527 laboratory test data of four types of weirs, namely, Normal and Inverted orientation Labyrinth Weirs in flume (NLW, ILW) and Arced Labyrinth Weirs with and without nappe Breakers in reservoir (ALW, ALWB), were captured from the published literature and utilized to feed the SVM-based models. The obtained results revealed the capability of the SVM-based models in determining discharge coefficients. The results showed that the SVM-based model of arced labyrinth weir (ALW) produced the most accurate results when three dimensionless parameters, e.g. (HT/P) head water ratio, (α/θ) angle ratio and (Lc/W) magnification ratio, were introduced as input parameters (Root mean square error [RMSE]= 0.013 and R2 = 0.970 for the test stage). Nonetheless, sensitivity analysis showed that Froude number and head water ratio are the most influential parameters on discharge coefficients of the labyrinth and arced labyrinth weirs, respectively.

Observations of Surface Wave–Current Interaction

AbstractWave–current interaction can result in significant inhomogeneities of the ocean surface wave field, including modulation of the spectrum, wave breaking rates, and wave statistics. This study presents novel airborne observations from two experiments: 1) the High-Resolution Air–Sea Interaction (HiRes) experiment, with measurements across an upwelling jet off the coast of Northern California, and 2) an experiment in the Gulf of Mexico with measurements of waves interacting with the Loop Current and associated eddies. The significant wave height and slope varies by up to 30% because of these interactions at both sites, whereas whitecap coverage varies by more than an order of magnitude. Whitecap coverage is well correlated with spectral moments, negatively correlated with the directional spreading, and positively correlated with the saturation. Surface wave statistics measured in the Gulf of Mexico, including wave crest heights and lengths of crests per unit surface area, show good agreement with second-order nonlinear approximations, except over a focal area. Similarly, distributions of wave heights are generally bounded by the generalized Boccotti distribution, except at focal regions where the wave height distribution reaches the Rayleigh distribution with a maximum wave height of 2.55 times the significant wave height, which is much larger than the standard classification for extreme waves. However, theoretical distributions of spatial statistics that account for second-order nonlinearities approximately bound the observed statistics of extreme wave elevations. The results are discussed in the context of improved models of breaking and related air–sea fluxes.

On dispersion of directional surface gravity waves

Using a nonlinear evolution equation we examine the dependence of the dispersion of directional surface gravity waves on the Benjamin–Feir index (BFI) and crest length. A parameter for describing the deviation between the dispersion of simulated waves and the theoretical linear dispersion relation is proposed. We find that for short crests the magnitude of the deviation parameter is low while for long crests the magnitude is high and depends on the BFI. In the present paper we also consider laboratory data of directional waves from the Marine Research Institute of the Netherlands (MARIN). The MARIN data confirm the simulations for three cases of BFI and crest length.

Ambient Vibration Tests at Some Buttress Dams in Romania

The paper presents a selection of results from ambient vibration tests performed during the period 2015 – 2016 at three buttress dams in Romania. The following buttress dams were investigated: (i) Stramtori - Firiza dam on Firiza River (52 m height, 198m crest length), (ii) Gura Raului dam on Cibin River (74 m height, 328m crest length), (iii) Poiana Uzului dam on Uz River (84 m height, 507m crest length). Vibration data were acquired in two dam operation conditions: with and without running of hydro-mechanical equipment. The vibration measurement equipment and setups, the processing of the recorded data and the obtained results (through spectral analysis) are presented. The main modal frequencies of the investigated buttress dams were estimated. The modal properties are considered for the monitoring of dams’ dynamic behavior for small amplitude vibrations (elastic behavior) and for the calibration of the numerical associated models. The measurements campaigns are part of the long-term monitoring of dams. If such investigation program is repeated every 3÷5 years, the dams ambient vibration response can be used for the assessment of the structural and/or material degradation, due to ageing or to other alteration processes. As Romania is an earthquake prone country, such results can also be used as a witness of the dam’s status before a major seismic event.

Run-up heights of solitary waves on a circular island with asymmetric crest lengths

최근 기후변화에 효과적으로 대응하기 위해서 신뢰성 높은 설계홍수량을 산정할 필요성이 커지고 있다. 본 연구에서는 홍수빈도해석법과 설계 강우-유출 관계 분석법으로 산정되는 확률홍수량의 차이를 분석하였다. 우리나라의 경우 관측유량 자료가 부족하여 설계홍수량을 결정할 때 설계 강우-유출 관계 분석법으로 산정된 확률홍수량을 이용하고 있다. 관측 유량 자료를 활용한 홍수빈도해석법의 결과를 참값으로 가정하여 분석한 결 과, 설계강우-유출 관계 분석법으로 산정된 확률홍수량은 홍수빈도해석법으로 산정된 확률홍수량에 비해 약 79% 과대 산정되는 것으로 나타났 다. 따라서, 본 연구에서는 설계강우-유출 관계 분석법으로 산정된 확률홍수량을 보정하는 회귀곡선식을 개발하였다. 이를 위해 우리나라 8개 댐 유역의 강우와 유량자료를 획득한 후, 비선형 회귀분석을 통하여 보정식을 제안하였다. 본 연구에서 제안한 보정식을 적용할 경우, 설계강우-유출 관계 분석법으로 산정된 확률홍수량보다 평균적으로 정확도가 약 65.0% 향상되었다. 또한, 유역의 크기를 고려하면, 유역의 크기를 고려하지 않 았을 때보다 평균적으로 정확도가 약 2.1%p 증가하였다.

Comparison the hydraulic characteristics of finite crest length weir with quarter-circular crested weir

Weirs are used for flow measurement, flow diversion and water level control in open channels. In this study, experiments were conducted on finite crest length weir and quarter-circular crested weir and hydraulic characteristics of two weirs were compared together. Depending on the ratio of total upstream head H to weir crest length L, flow over the finite crest length weir was undular, parallel to the crest surface or curvilinear. Also, for H/L>1.82, lower nappe separated from the upstream corner of crest and did not reattach to the crest surface. In the range of conducted tests (H/L<2.20), flow over the quarter-circular crested weir was curvilinear and lower nappe did not separate from the crest surface. Due to the elimination of separation zone, which is the primary source of energy loss, discharge coefficient for quarter-circular crested weir is significantly larger than for finite crest length weir. Furthermore, negative (sub-atmospheric) pressure on the crest surface of finite crest length weir and quarter-circular crested weir occurred for H/L>1.52 and H/L>2.2, respectively. This result indicates that quarter-circular crested weir is less sensitive to cavitation danger.

Air entrainment and bubble statistics in breaking waves

We investigate air entrainment and bubble statistics in three-dimensional breaking waves through novel direct numerical simulations of the two-phase air–water flow, resolving the length scales relevant for the bubble formation problem, the capillary length and the Hinze scale. The dissipation due to breaking is found to be in good agreement with previous experimental observations and inertial scaling arguments. The air entrainment properties and bubble size statistics are investigated for various initial characteristic wave slopes. For radii larger than the Hinze scale, the bubble size distribution, can be described by $N(r,t)=B(V_{0}/2{\rm\pi})({\it\varepsilon}(t-{\rm\Delta}{\it\tau})/Wg)r^{-10/3}r_{m}^{-2/3}$ during the active breaking stages, where ${\it\varepsilon}(t-{\rm\Delta}{\it\tau})$ is the time-dependent turbulent dissipation rate, with ${\rm\Delta}{\it\tau}$ the collapse time of the initial air pocket entrained by the breaking wave, $W$ a weighted vertical velocity of the bubble plume, $r_{m}$ the maximum bubble radius, $g$ gravity, $V_{0}$ the initial volume of air entrained, $r$ the bubble radius and $B$ a dimensionless constant. The active breaking time-averaged bubble size distribution is described by $\bar{N}(r)=B(1/2{\rm\pi})({\it\epsilon}_{l}L_{c}/Wg{\it\rho})r^{-10/3}r_{m}^{-2/3}$, where ${\it\epsilon}_{l}$ is the wave dissipation rate per unit length of breaking crest, ${\it\rho}$ the water density and $L_{c}$ the length of breaking crest. Finally, the averaged total volume of entrained air, $\bar{V}$, per breaking event can be simply related to ${\it\epsilon}_{l}$ by $\bar{V}=B({\it\epsilon}_{l}L_{c}/Wg{\it\rho})$, which leads to a relationship for a characteristic slope, $S$, of $\bar{V}\propto S^{5/2}$. We propose a phenomenological turbulent bubble break-up model based on earlier models and the balance between mechanical dissipation and work done against buoyancy forces. The model is consistent with the numerical results and existing experimental results.

EXPERIMENTAL INVESTIGATION OF THE APPROACH ANGLE EFFECTS ON THE DISCHARGE EFFICIENCY FOR BROAD CRESTED WEIRS

In open channels broad crested weirs are widely used to measure the discharge values. In this study the effect of the approach angle on the discharge efficiency of the broad crested weir was investigated experimentally. Four different approach angles were tested under steady state conditions by using three different discharge values. Experimental results indicate that the discharge coefficient is not only a function of crest length but also a function of approach angle. A modified new non dimensional empirical relation involved approach angle has been proposed.

Dietary adaptations in the teeth of murine rodents (Muridae): a test of biomechanical predictions

Functional dental theory predicts that tooth shape responds evolutionarily to the mechanical properties of food. Most studies of mammalian teeth have focused on qualitative measures of dental anatomy and have not formally tested how the functional components of teeth adapt in response to diet. Here we generated a series of predictions for tooth morphology based on biomechanical models of food processing. We used murine rodents (Old World rats and mice) to test these predictions for the relationship between diet and morphology and to identify a suite of functional dental characteristics that best predict diets. One hundred and five dental characteristics were extracted from images of the upper and lower tooth rows and incisors for 98 species. After accounting for phylogenetic relationships, we showed that species evolving plant-dominated diets evolved deeper incisors, longer third molars, longer molar crests, blunter posteriorly angled cusps, and more expanded laterally oriented occlusal cusps than species adapting to animal-dominated diets. Measures of incisor depth, crest length, cusp angle and sharpness, occlusal cusp orientation, and the lengths of third molars proved the best predictors of dietary adaptation. Accounting for evolutionary history in a phylogenetic discriminant function analysis notably improved the classification accuracy. Molar morphology is strongly correlated with diet and we suggest that these dental traits can be used to infer diet with good accuracy for both extinct and extant murine species.

Pattern analysis of a linear dune field on the northern margin of Qarhan Salt Lake, northwestern China

In terms of formation mechanisms of linear dunes, there are open arguments for their widespread distribution and multi-morphological diversities. In order to clarify the formation mechanism of linear dunes of Qarhan Salt Lake, we used pattern analysis method to analyze the statistical characteristics and spatial variation of their pattern parameters. Except at the west-northwest margin, the pattern parameters showed regular spatial variation from the up-middle part towards the downwind end of the dune field. Based on the cumulative probability plots for inter-crest spacing and crest length, we divided the linear dunes into three groups, which corresponding to the three evolution stages of these dunes. The first group comprises erosional relics, with shorter crests, smaller inter-crest spacing and more random dune orientation. The second group comprises dunes whose sand supply is just sufficient to maintain stability and these dunes are approaching the net erosion stage. The crest length and inter-crest spacing of these dunes are much larger than those of the first group, and dune orientation is closer to the resultant drift direction (RDD). The last group comprises linear dunes that are still undergoing vertical accretion and longitudinal elongation, which follows the RDD of the modern wind regime. The presence of regular spatial variation of pattern parameters and a similar geometry with the vegetated linear dunes suggest that deposition and erosion coexist in the development and evolution of linear dunes of Qarhan Salt Lake, i.e. deposition predominates at the downwind end of linear dunes in the vertical accretion and longitudinal elongation stage, whereas erosion mainly occurs at the upwind end of linear dunes in the degradation stage. Therefore, the formation mechanism of linear dunes in Qarhan Salt Lake can be reasonably explained by the combination of depositional and erosional theories.

THE ANALYSIS OF WATER RELEASE FROM THE HYDRO ACCUMULATION LAKE MODRAC WITH SPILLWAY CURVE AND VOLUME CURVES

&amp;lt;p&amp;gt;Dam Modrac is multiple arched reinforced concrete buttress dam, with nine buttresses and ten arches, which by its technical characteristics and volume of the accumulation is considered as one of the high dams. Crown level of spillway is 200.00 m a.s.l. Crest length is 205.00 m, while the maximum height is 27.50 m. To control the water level in the reservoir, under normal hydrological conditions, there are four basic discharges with maximum capacity around Q = 77 m3 /s for the projected state. The paper gives an analytical expression of the spillway curve and analytical expressions of amounts of water discharge separately for each bottom outlet, which are obtained by conducted measurings. Special significance of this paper gives volume curves for hydro accumulation Lake Modrac for projected state and the period of use of the system.&amp;lt;/p&amp;gt;

Genetic Variation within Iranian Iris Species Using Morphological Traits

Iris belongs toIridaceae family and it is monocotyledon. Iris is one of the important ornamental and medicinal plants. 34 iris genotypes (14 species) collected from different provinces of Iran were planted at National Institute of Ornamental Plants (NIOP) Iran. All of the species evaluated for 15 quantitative traits and 30 qualitative traits. Results showed that the highest positive correlation was between inner tepal length and width and the lowest of this correlation was between crest length and width. Cluster analysis using Ward similarity coefficient divided Iris species into three clusters. Also the highest Nei’s genetic distance based on qualitative traits was between I. iberica and I. fosterana and the lowest was between I. germanica and I. paradoxa. The maximum genetic diversity was in Khorasan Razavi populations, and the minimum was in Khorasan (North). According to Shannon index, I. spuria and I. germanica species had the maximum level of genetic diversity. Cluster analysis according to qualitative traits by Jaccard similarity coefficient and UPGMA classified the 34 genotypes into four groups. Classification of populations based on quantitative traits was not similar to classification based on qualitative traits and they were not similar to geographical distribution.

Dyke overtopping: effects of shape and headwater elevation

ABSTRACTThis study deals with the erosion of granular laboratory dykes to allow for the prediction of the main dyke failure features, including the temporal advance of the maximum dyke height and the breach discharge. Two extreme scenarios are considered: (1) constant approach flow discharge; and (2) constant headwater elevation during the breach process, as the two extreme cases of prototype scenarios. Based on the previous research, the effects of three additional parameters, namely the up- and downstream dyke face slopes and the crest length, are considered by the so-called dyke shape parameter. Its effect is included in the governing dyke breach equations so that all relevant variables vary only as a function of discharge scenario, original dyke height, and sediment diameter. The breach process is described with typical images and plots, to highlight the various effects. The results allow for an estimate of the dyke breach characteristics based on Froude similitude.

Age-related changes in molar topography and shearing crest length in a wild population of mountain Gorillas from Volcanoes National Park, Rwanda.

Great ape teeth must remain functional over long lifespans. The molars of the most folivorous apes, the mountain gorillas, must maintain shearing function for 40+ years while the animals consume large quantities of mechanically challenging foods. While other folivorous primates experience dental senescence, which compromises their occlusal surfaces and affects their reproductive success as they age, it is unknown whether dental senescence also occurs in mountain gorillas. In this article, we quantified and evaluated how mountain gorilla molars change throughout their long lifespans. We collected high-resolution replicas of M(1)s (n = 15), M(2)s (n = 13), and M(3)s (n = 11) from a cross-sectional sample of wild mountain gorilla skeletons from the Virunga Volcanoes, ranging in age from 4 to 43 years. We employed dental topographic analyses to track how aspects of occlusal slope, angularity, relief index, and orientation patch count rotated change with age. In addition, we measured the relative length of shearing crests in two- and three-dimensions. Occlusal topography was found to decrease, while 2D relative shearing crest length increased, and 3D relative crest lengths were maintained with age. Our findings indicate that shearing function is maintained throughout the long lifetimes of mountain gorillas. Unlike the dental senescence experienced by other folivorous primates, mountain gorillas do not appear to possess senesced molars despite their long lifetimes, mechanically challenging diets, and decreases in occlusal topography with age.

Using Energy Dissipation Rate to Obtain Active Whitecap Fraction

AbstractActive and total whitecap fractions quantify the spatial extent of oceanic whitecaps in different lifetime stages. Total whitecap fraction W includes both the dynamic foam patches of the initial breaking and the static foam patches during whitecap decay. Dynamic air–sea processes in the upper ocean are best parameterized in terms of active whitecap fraction WA associated with actively breaking crests. The conventional intensity threshold approach used to extract WA from photographs is subjective, which contributes to the wide spread of WA data. A novel approach of obtaining WA from energy dissipation rate ε is proposed. An expression for WA is derived in terms of energy dissipation rate WA(ε) on the basis of the Phillips concept of breaking crest length distribution. This approach allows more objective determination of WA using the breaker kinematic and dynamic properties yet avoids the use of measuring breaking crest distribution from photographs. The feasibility of using WA(ε) is demonstrated with one possible implementation using buoy data and a parametric model for the energy dissipation rate. Results from WA(ε) are compared to WA from photographic data. Sensitivity analysis quantifies variations in WA estimates caused by different parameter choices in the WA(ε) expression. The breaking strength parameter b has the greatest influence on the WA(ε) estimates, followed by the breaker minimal speed and bubble persistence time. The merits and caveats of the novel approach, possible improvements, and implications for using the WA(ε) expression to extract WA from satellite-based radiometric measurements of W are discussed.

ESTIMATION OF THE NEARSHORE WAVE PARAMETERS USING AN ITNERFEROMETRIC SAR

Nearshore areas of seas and oceans have been always of especial importance for the life activity of most people. Along with the stabilizing factor of the weather and climate associated with the close vicinity of water, the sea-land boundary is characterized by appearance of specific gradients and flows of heat, moisture, pressure etc. These can cause weather hazards which are necessary to be monitored and predicted. The basis of the purposeful study of the impact of natural and anthropogenic factors on the coastal zones and, in particular, on the shore areas, is monitoring of the coastal processes. Among modern methods of environmental monitoring the remote sensing techniques seem to be especially promising ones. The paper presents results of radar sounding of the nearshore area near the New River mouth (North Carolina, USA) with the use of a synthetic-aperture radar (SAR). The nearshore wave parameters, such as wave height, phase velocity, wave crest length etc. are estimated from the SAR images. An algorithm is suggested for determining the width and shape of the spectrum of the radial component of water drops in breaking waves. The range of radial velocities of the drops is analyzed in dependence on the significant wave height.

Numerical Modeling of Flow Over Two Side Weirs

Nowadays, due to the significant development of hydraulic models, it is possible to investigate miscellaneous hydraulic phenomena and reveal the extent to which their changes in a particular parameter will affect the flow condition without the need of extra experiments. In the present study, flow patterns over a side weir were studied both experimentally and numerically. The experiments were done for a side weir with the length of 4m. However, in the numerical model, the 4m weir was replaced with two side weirs with the length of 2m which were placed within two meters distance from each other. The primary contributions of the paper are to show that a numerical model can be used to simulate the flow over both single and double side weirs, and to quantify the increased discharge from two side weirs relative to discharge from a single side weir having the same crest length as the two side weirs.