انجمن هیدرولیک ایران
نشریه هیدرولیک
2345-4237
3
3
2008
11
21
An Investigation into the Effects of the Experimentation Scale Upon Unsteady Non-Darcy Flows Through Rubble Mound Breakwaters
بررسی اثر مقیاس در مطالعه آزمایشگاهی جریان های غیردارسی غیرماندگار گذرنده از موج شکن های توده سنگی
1
13
85470
10.30482/jhyd.2008.85470
FA
صدف
نظافت خواه
حبیب الله
بیات
Journal Article
2008
03
22
As the pore pressure within core materials in rubble mound breakwaters affect the armours stability, it<br />is often necessary to consider scale effects when related designs call for a hydraulic model study based<br />on the Froude criterion. This paper describes findings of an analytical evaluation of unsteady<br />transitional flow regimes through coarse porous media in an attempt to develop a modelling law based<br />on similarities between hydraulic behaviours of the model and the prototype. A non-linear analysis<br />approach based on the so-called modified Forschhiemer equation has been employed in developing<br />necessary equations needed for scale effects assessments. It has been made clear that the grains scale<br />ratio is not a constant and its power varies with variations of the flow regime. The extent of the<br />validity of findings in enabling correct interpretation of experimental results have been examined<br />using available field data published by previous researchers for rubble mound structures.
https://jhyd.iha.ir/article_85470_b0f970f287ac2d861151c8960040d7a1.pdf
انجمن هیدرولیک ایران
نشریه هیدرولیک
2345-4237
3
3
2008
11
21
Effect of Slot on Stability of Riprap around Bridge Piers
تاثیر شکاف پایه بر پایداری سنگ چین در اطراف پایه های استوانه ای پل ها
15
28
85471
10.30482/jhyd.2008.85471
FA
منوچهر
حیدرپور
پروفسور منوچهر حیدرپور/استاد تمام دانشگاه صنعتی اصفهان
بهزاد
قربانی
ملیحه
کیخائی
رحیم
پیرمحمدی
Journal Article
2008
03
22
An accepted engineering method to deal with local scouring at bridge piers is to place riprap material<br />around the pier foundation. Field experience has shown that riprap stones often disappear with time,<br />with most severe failure occurring during floods; and refilling is frequently needed to replenish the<br />lost stones. Therefore, notice to riprap stability is necessary and has been the aim of this paper. In this<br />research, four sizes of riprap located above, the same level and below the surface of the streambed and<br />two slot sizes continued to the streambed were used. Effect of presence and size of slot on riprap<br />stability and minimum necessary dimensions for finished riprap covering have been studied. The<br />results obtained in the experiments range; show that riprap is more stable when using slot and this<br />stability is more evident with bigger slot. The performance of the two slot sizes decreases when using<br />the bigger stones. Decrease in performance of the big slot using the bigger stones is more than that of<br />the small slot. Furthermore, results show that the slot decreases the finished riprap covering and<br />consequently the riprap volume will decrease effectively. It has been found that the riprap placed<br />above and below the streambed have the most and the lowest stability, respectively.
https://jhyd.iha.ir/article_85471_1f0b373fa964784bf9d8b8a379832b7b.pdf
انجمن هیدرولیک ایران
نشریه هیدرولیک
2345-4237
3
3
2008
11
21
Effects of Bed Roughness Shape on the Length of Hydraulic Jump
تاثیر شکل زبری بستر بر طول پرش هیدرولیکی در کانال های مستطیلی
29
40
85472
10.30482/jhyd.2008.85472
FA
محمود
شفاعی بجستان
دانشگاه شهید چمران اهواز
کبری
نیسی
Journal Article
2008
03
22
In this study, effects of shape of roughness elements on the length of hydraulic jump have<br />been investigated experimentally. For the purpose of this study, prismatic roughness elements<br />with different shapes (rectangular, triangular, circular, lozenge and hexangular) have been<br />tested in a rectangular flume 7.5m long and 30cm wide. Experiments were performed in the<br />hydraulic laboratory of Shahid Chamran University, Ahwaz, Iran. The roughed elements are<br />glued on the bed of flume downstream of ogee spillways in such a way that the incoming<br />water jet is just above the element surface. It should be noted that in previous studies the<br />rough elements have been tested such that the incoming jet was at the same level of the<br />element bottom so the elements act as baffle blocks. Each rough element was tested under<br />different flow conditions. The incoming Froude number was in the range of 4.5 to 12. During<br />each test the water surface profile, the roller length and the jump length were measured. In<br />few tests the longitudes and vertical flow velocity were measured. The results indicate that the<br />presence of rough element can reduce the hydraulic jump length and the amount of the<br />reduction depends on the Froude number and the roughness shape. The lozenge element shape<br />was found to produce lesser jump length (up to 40% of the smooth bed jump). Relations have<br />been presented in this study to predict jump length, roller length and the amount of energy<br />which is dissipated. Comparison of this study with previous results reveals that using the<br />rough element can reduce the hydraulic jump as much as the block elements do, and the rough<br />element can not cause separation of flow which might be subject to cavitations.
https://jhyd.iha.ir/article_85472_2a4e307d55b09dc3873ac73064f858ce.pdf
انجمن هیدرولیک ایران
نشریه هیدرولیک
2345-4237
3
3
2008
11
21
Experimental Study of 3D Flow Field and Scour in a 90 Degree Bend
مطالعه آزمایشگاهی الگوی جریان سه بعدی و آبشستگی در قوس 90 درجه
41
57
85473
10.30482/jhyd.2008.85473
FA
محمد
واقفی
مسعود
قدسیان
سید علی اکبر
صالحی نیشابوری
Journal Article
2008
03
22
Flow is affected by both the pressure gradient and the centrifugal forces in the bend of rivers and their<br />interaction leads to secondary flow. In this study the flow field and scour in a 90 degree bend were<br />experimentally measured. Experiments were carried out in a channel with mild curvature. A threedimensional<br />Acoustic Doppler Velocimeter (ADV) was used for measuring the flow field. Also, a<br />laser bed profiler was used for measuring the variation of bed topography. The results show formation<br />of a main secondary flow in the bend and another second secondary flow near the outer bank. The<br />direction of the second secondary flow is opposite to the direction of the main secondary flow. This<br />flow pattern is evident from the middle sections of the first half of the bend up to the end of the bend.<br />The results of flow pattern and bed scour were also addressed. In addition, the vortices in the bend, the<br />changes in the secondary flow and the vortices and the scour pattern at the outer bank and<br />sedimentation at the inner bank are investigated.
https://jhyd.iha.ir/article_85473_d9a24f4e004583aed12d01f22704c6d2.pdf
انجمن هیدرولیک ایران
نشریه هیدرولیک
2345-4237
3
3
2008
11
21
Upwind Finite Volume Solution of Water Hammer in Pipes without Column Separation in Unsteady Friction Model
اصطکاک ناماندگار در تحلیل حجم محدود جهتمند پدیده ضربه قوچ در لوله ها در شرایط عدم جدایی توده آب
59
65
85474
10.30482/jhyd.2008.85474
FA
علی
عباسی
0000-0001-7098-3717
سعید رضا
صباغ یزدی
دانشکده مهندسی عمران دانشگاه صنعتی خواجه نصیرالدین طوسی
Journal Article
2008
03
22
The waves resulting from instantaneous and complete valve-closure in pressurized pipe systems,<br />propagate upstream and/or downstream in the hydraulic system .The pressure (head) and velocity of<br />the flow (waves) are important parameters in the design of pipeline systems. A simple and efficient<br />approximation to the Vardy–Brown unsteady friction equation is implemented within a FVM solution<br />for unsteady pipe flows. The model is compared with measured data and numerical data produced by a<br />two-dimensional turbulence water-hammer model. The results show that the model is in good<br />agreement with both laboratory and numerical results. The computed minimum and maximum values<br />and the time period of the pressure waves are in close agreement with the 2-D numerical solution and<br />experimental measurements.
https://jhyd.iha.ir/article_85474_d21ad8d526652d521e8c025cf844f38a.pdf