In this paper, the outflow process of a linear width contraction device for a free-flow condition is modeled using the dimensional analysis and the incomplete self-similarity condition. The proposed theoretical stage-discharge relationship is tested using measurements available in the literature. The proposed power stage-discharge equation is characterized by a value of the exponent close to 2 and a coefficient depending on the angle of the device sides with the channel bank. The proposed flume is characterized by simple construction, easy installation, low cost, and a good accuracy of the measured discharge (errors in the estimate ranging from − 3.84 to 1.9%). The deduced stage-discharge equation is characterized by errors in the estimate of discharge lower than or equal to ± 3% for 93.7% of the investigated cases. The main result of this paper is a stage-discharge relationship giving an accurate estimate of discharge but, at the same time, having the advantage of working regardless of the discharge coefficient estimate.

本文利用量纲分析和不完全自相似条件对自由流动条件下线性宽度收缩装置的流出过程进行了建模。使用文献中提供的测量结果来测试所提出的理论阶段-放电关系。所提出的功率级放电方程的特点是指数值接近2，系数取决于器件侧面与通道组的角度。所提出的水槽具有结构简单、安装方便、成本低、流量测量精度高（估算误差范围为−3.84%至1.9%）的特点。推导的阶段流量方程的特点是，在 93.7% 的调查案例中，流量估计误差低于或等于 ± 3%。