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Water 2015, 7(9), 4951-4970;

Dynamic Lift on an Artificial Static Armor Layer During Highly Unsteady Open Channel Flow

Department of Hydraulic and Environmental Engineering, Norwegian University of Science andTechnology, S.P. Andersens veg 5, Trondheim 7491, Norway
Department of Civil and Environmental Engineering, The University of Auckland, 20 SymondsStreet, Auckland 1010, New Zealand
These authors contributed equally to this work.
Author to whom correspondence should be addressed.
Academic Editor: Thorsten Stoesser
Received: 8 July 2015 / Revised: 5 September 2015 / Accepted: 6 September 2015 / Published: 14 September 2015
(This article belongs to the Special Issue Recent Advances in Riverflow Research)
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The dynamic lift acting on a 100 mm × 100 mm section of a static armor layer during unsteady flow is directly measured in a series of physical experiments. The static armor layer is represented by an artificial streambed mold, made from an actual gravel bed. Data from a total of 190 experiments are presented, undertaken in identical conditions. Results show that during rapid discharge increases, the dynamic lift on the streambed repeatedly exhibits three clear peaks. The magnitude of the observed lift depends on the following hydrograph characteristics: (1) the initial flow depth; (2) the ramping duration and therefore the ramping rate; and (3) the total discharge increase. An adjusted unsteadiness parameter combines those three hydrograph characteristics for rapid discharge increases. Direct correlations between the unsteadiness parameter and the measured dynamic lift during unsteady flow are presented. In addition, the armor layer porosity showed a major impact on the observed effects. It is shown that increasing bed porosity leads to decreasing dynamic lift. View Full-Text
Keywords: lift force; artificial streambed; force sensor; load cell; unsteady flow lift force; artificial streambed; force sensor; load cell; unsteady flow

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Spiller, S.M.; Rüther, N.; Friedrich, H. Dynamic Lift on an Artificial Static Armor Layer During Highly Unsteady Open Channel Flow. Water 2015, 7, 4951-4970.

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