Rijit davranış gösteren esnek bitkilerin akıma karşı oluşturduğu direncin belirlenmesi

Year 2017, Volume: 23 Issue: 6, 732 - 740, 15.12.2017

Gökçen Bombar Ebru Eriş , Üveys Kavaklı

Abstract

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.

Keywords

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

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