Rijit davranış gösteren esnek bitkilerin akıma karşı oluşturduğu direncin belirlenmesi

Öz

Bu çalışmada farklı dizilimlerde yerleştirilen çok saplı esnek bitkilerin akıma karşı dik durarak rijit davranış göstermesi durumunda oluşturacağı pürüzlülük katsayılarının elde edilmesi amaçlanmıştır. Dört farklı konfigürasyonda gerçekleştirilen 166 deneyde 7 farklı noktada akım derinliği ölçülmüş, debi elde edilmiş ve bitkilerden ötürü kaynaklanan yük kaybı hesaplanmıştır. Chézy katsayısı , Darcy-Weisbach sürtünme katsayısı  ve Manning katsayısı ’in, Reynolds sayısının 10000 değerinden küçük ve büyük olması durumunda tek bir fonksiyonla ifade edilemeyeceği görülmüş ve veriler iki gruba ayrılarak incelenmiştir. Pürüzlülük katsayısını verecek boyutsuz parametreler Froude sayısı , Reynolds sayısı , bağıl pürüzlülük , yaklaşım akımı enerji çizgisi eğimi  ve bitki yoğunluğu  olarak belirlenmiştir. Pürüzlülük katsayılarının belirlenmesi için doğrusal olmayan regresyon modeli ile en uygun denklemler elde edilmiştir. Reynolds sayısının 10000’den küçük olması durumunda pürüzlülük katsayıları için; f=f{h/hv}, n={Fr,h/hv,k}  ve C={Fr, Sf}  olduğu; Reynolds sayısının 10000’den büyük olması durumunda f={h/hv,k}, n={Fr,h/hv,k} ve C={Fr, Re, h/hv, Sf, k} olduğu görülmüştür. Ayrıca beklendiği gibi düşük Reynolds sayılarında bitkilerin varlığının, diğer parametrelerden bağımsız olarak akıma karşı gösterilen direnci arttırdığı sonucuna varılmaktadır. Bu denklemlerdeki farklı katsayıların akım doğrultusundaki bitki yüzey alanı ve bitki yoğunluğu gibi faktörlerden etkilendiği düşünülmektedir.

Anahtar Kelimeler

• Bitki,Esnek,Batık olmayan,Akıma karşı direnç,Pürüzlülük katsayıları

Determination of flexible vegetation resistance against the flow with rigid behavior

Abstract

In this study, it is aimed to obtain roughness coefficients of flexible multi-stemmed vegetation standing upright against flow with rigid behavior. Flow depths and discharges are measured; head losses causing from vegetation are calculated at 7 different points in 166 experiments for four different configurations. It is seen that Chézy coefficient , Darcy-Weisbach friction coefficient  and Manning coefficient  cannot be expressed with a single function for all Reynolds number. Therefore, the data are analyzed for the two different cases of Reynolds number lower and greater than 10000. Dimensionless parameters for the roughness coefficients are determined as Froude number , Reynolds number , the relative roughness , approach flow energy line slope , and vegetation density . The most suitable equations for estimating roughness coefficients are obtained by non-linear regression models. It is evaluated that for the Reynolds number lower than 10000 the roughness coefficients are defined as f=f{h/hv}, n={Fr,h/hv,k} and C={Fr, Sf} , and for the Reynolds number greater than 10000 they are given as f={h/hv,k}, n={Fr,h/hv,k} and C={Fr, Re, h/hv, Sf, k}. Also, for relatively low Reynolds numbers, the presence of plants caused an increase in resistance against the flow independently of other parameters as expected. It is observed that the regression equation coefficients could be influenced by factors such as surface area plant in the flow direction and plant density.

Keywords

• Vegetation,Flexible,Emergent,Resistance to flow,Roughness coefficients

Kaynakça

1. Jarvela J. “Effect of Submerged Flexible Vegetation on Flow Structure and Resistance”. Journal of Hydrology, 307(1-4), 233-241, 2005.
2. Tsujimoto T. “Fluvial Processes in Streams with Vegetation”. Journal of Hydraulic Research, 37(6), 789-803, 1999.
3. Galema A. Vegetation Resistance: Evaluation of Vegetation Resistance Descriptors for Flood Management. MSc Thesis, University of Twente, Netherlands, 2009.
4. Stone MB, Shen HT. “Hydraulic Resistance of Flow in Channels with Cylindrical Roughness”. Journal of Hydraulic Engineering, 128(5), 500-506, 2002.
5. Kleinhans, M. “Hydraulic Roughness” http://www.geo.uu.nl/fg/mkleinhans/teaching/rivmorrough.pdf (15.03.2016).
6. Chow VT. Open-Channel Hydraulics. New York, Tokyo, McGraw-Hill, 1959.
7. Wu FC, Shen HW, Chou YJ. “Variation of Roughness Coefficients for Unsubmerged and Submerged Vegetation”. Journal of Hydraulic Engineering, 125(9), 834-842, 1999.
8. Wilson CAME, Horritt MS. “Measuring the Flow Resistance of Submerged Grass”. Hydrological Processes, 16, 2589-2598, 2002.

9. Palmer VJ. “A Method for Designing Vegetated Waterways”. Agriculture Engineering, 26(12), 516-520, 1945.
10. Kouwen N, Li RM, Simons DB. “Flow Resistance in Vegetated Waterways”. Transactions ASME, 24(3), 684-698, 1981.
11. Ree WO, Crow FR. “Friction Factors for Vegetated Waterways of Small Slope”. Agricultural Research Service, US Department of Agriculture, Technical Report Publication S-151, 1977.
12. Armanini A, Righetti M, Grisenti P. “Direct Measurement of Vegetation Resistance in Prototype Scale”. Journal of Hydraulic Research, 43(5), 481-487, 2005.
13. Wilson CA, Hoyt J, Schnauder I. “Impact of Foliage on the Drag Force Vegetation in Aquatic Flows”. Journal of Hydraulic Engineering, 134(7), 885-891, 2005.
14. Schnauder I, Wilson CA. Discussion “Direct Measurement of Vegetation Resistance in Prototype Scale”. Journal of Hydraulic Research, 47(3), 384-386, 2009.
15. Oplatka M. Stabiltaet von Weidenverbauungen an Flussfern, PhD Thesis, TH Zurich, Switzerland, 1998.
16. Xavier P, Wilson C, Aberle J, Rauch HP, Schoneboom T, Lammeranner W, Thomas H. “Drag force of flexible submerged trees”. Proceedings of the HYDRALAB III Join User Meeting, Hannover, 2-4 February, 2010.
17. Kouwen N, Unny TE, Hill HM. “Flow Retardance in Vegetated Channels”. Journal of Irrigation Drainage Engineering, 95(2), 329-344, 1969.
18. Kummu M. Roughness Characteristics and Velocity Profile in Vegetated and Nonvegetated Channel, MSc Thesis, Helsinki University of Technology, Greece, 2002.
19. Temple DM. “Flow Retardance of Submerged Grass Channel Linings”. Transactions, American Society of Agricultural Engineers, 25(5), 1300-1303, 1982.
20. Darby SE. “Effect of Riparian Vegetation on Flow Resistance and Flood Potential”. Journal of Hydraulic Engineering, 125(5), 443-454, 1999.
21. Kouwen N, Li RM. “Biomechanics of Vegetative Channel Linings”. Journal of Hydraulic Engineering, 106(6), 1085-1103, 1980.
22. Kouwen N. “Field Estimation of the Biomechanical Properties of Grass”. Journal of Hydraulic Research, 26(5), 559-568, 1988.
23. Eastgate WI. Vegetated Stabilization of Grassed Waterways and Dam bywashes, MSc Thesis, University of Queensland, St. Lucia, Queensland, Australia, 1966.
24. Masterman R, Thorne CR. Analytical Approach to Flow Resistance in Gravel-Bed Channels with Vegetated Banks. Editors: Kirkby, MJ. Process Models and Theoretical Geomorphology. 201-218, Chichester, England, Wiley, 1994.
25. Albayrak İ, Nikora V, Miler O, O’Hare M. “Flow-plant Interactions at a Leaf Scale: Effects of Leaf Shape, Serration, Roughness and Flexural Rigidity”. Aquatic Sciences, 74(2), 267-286, 2012.
26. Miler O, Albayrak İ, Nikora V, O’Hare M. “Biomechanical Properties of Aquatic Plants and Their Effects on Plant-flow Interactions in Streams and Rivers”. Aquatic Science, 74(1), 31-44, 2012.
27. Baptist MJ, Babovic V, Rodrigues-Uthurburu J, Keijzer M, Uittenbogaard RE, Verway A, Mynett AE. “On Inducing Equations for Vegetation Resistance”. Journal of Hydraulic Research, 45(4), 435-450, 2006.
28. Chang L, Yong-Ming S. “Flow Structure and Sediment Transport with Impacts of Aquatic Vegetation”. Journal of Hydrodynamics, 20(4), 461-468, 2008.
29. Kothyari UC, Hashimoto H, Hayashi K. “Effect of Tall Vegetation on Sediment Transport by Channel Flows”. Journal of Hydraulic Research, 47(6), 700-710, 2009.
30. Eriş E, Bombar G, Kavaklı Ü. “Effect of Emergent Vegetation Distribution on Energy Loss”. IAHR 4th IAHR Europe Congress, Liege, Belgium, 27-29 July 2016.