Chapter 2
Similarity of Model Experiments
Abstract A successful experiment with a physical model requires necessary conditions of similarity. This chapter presents an experimental method with a semi-scale
physical model. Four criteria are mentioned here: similarities of watershed geometry,
grain size and bare land, Froude number (Fr) for rainfall event, and soil erosion in
the downscaled models. The efficacy of the proposed method was confirmed using
these criteria in two different downscaled model experiments. Experimental results
show that while the amount of soil loss in the small scale models was converted by
multiplying the scale number, the amount was very close to that of the large scale
model. Obviously, with a semi-scale physical model, the experiments are available
to verify and predict the soil loss in a catchment with the check dam system on the
Loess Plateau, China.
Keywords Loess Plateau · Check dam · Semi-scale model · Similarity condition ·
Soil loss
2.1 Development of the Experimental Erosion
Different from the monitoring or investigating method, an experiment of soil conservation under closely monitored or controlled experimental conditions focuses on
the regularities of soil loss from a micro perspective. According to the formation
of the underlying surface, the physical models may be categorized into two broad
classes, namely, in situ tests and laboratory experiments. Runoff and sediment distribution in a segment of the natural watershed may be conducted in an in situ test,
i.e. field experiment, under natural and simulated rainfall conditions to study the
mechanism of soil and water loss and the effects of management measures. As a
kind of representative field experiment, the runoff plot has been widely used all over
the world. The landform is not reconstructed although the border of the experimental
area should be strictly restricted in a field experiment. The processes of soil and water
loss under a complicated topographical condition may be relatively easily simulated
and observed in the field, because no change exists in the scales of the underlying
surface and properties of the erosion material. In contrast, a laboratory experiment,
i.e. model experiment, is performed in a scaled underlying surface reconstructed with
© Science Press and Springer Nature Singapore Pte Ltd. 2020
X. Xu et al., Experimental Erosion,
https://doi.org/10.1007/978-981-15-3801-8_2
7
Similarity of Model Experiments
Abstract A successful experiment with a physical model requires necessary conditions of similarity. This chapter presents an experimental method with a semi-scale
physical model. Four criteria are mentioned here: similarities of watershed geometry,
grain size and bare land, Froude number (Fr) for rainfall event, and soil erosion in
the downscaled models. The efficacy of the proposed method was confirmed using
these criteria in two different downscaled model experiments. Experimental results
show that while the amount of soil loss in the small scale models was converted by
multiplying the scale number, the amount was very close to that of the large scale
model. Obviously, with a semi-scale physical model, the experiments are available
to verify and predict the soil loss in a catchment with the check dam system on the
Loess Plateau, China.
Keywords Loess Plateau · Check dam · Semi-scale model · Similarity condition ·
Soil loss
2.1 Development of the Experimental Erosion
Different from the monitoring or investigating method, an experiment of soil conservation under closely monitored or controlled experimental conditions focuses on
the regularities of soil loss from a micro perspective. According to the formation
of the underlying surface, the physical models may be categorized into two broad
classes, namely, in situ tests and laboratory experiments. Runoff and sediment distribution in a segment of the natural watershed may be conducted in an in situ test,
i.e. field experiment, under natural and simulated rainfall conditions to study the
mechanism of soil and water loss and the effects of management measures. As a
kind of representative field experiment, the runoff plot has been widely used all over
the world. The landform is not reconstructed although the border of the experimental
area should be strictly restricted in a field experiment. The processes of soil and water
loss under a complicated topographical condition may be relatively easily simulated
and observed in the field, because no change exists in the scales of the underlying
surface and properties of the erosion material. In contrast, a laboratory experiment,
i.e. model experiment, is performed in a scaled underlying surface reconstructed with
© Science Press and Springer Nature Singapore Pte Ltd. 2020
X. Xu et al., Experimental Erosion,
https://doi.org/10.1007/978-981-15-3801-8_2
7