## 2 Materials and Methods  
In order to solve this problem, full-scale modeling of the processes of drilling waterjet channels was carried out using a specially designed laboratory bench. The process flow diagram of the developed test bench is shown in Figure 3.  
The flow diagram of the developed test bench (Figure 3) shows low-pressure pipelines and hoses in blue, and high-pressure sections in red. The high-pressure hydraulic laboratory bench operates as follows: the working disintegration agent is fed from the storage tank T-1 through ball valves 1 and 2 to the primary filtration unit consisting of two filters F-1 and F-2 installed in series. The letter designations \"P\" indicate pressure gauges. The rock disintegrating agent from the primary filtration unit is fed to the intake of Pump-1 high  
Figure 3: Process flow diagram of the developed test bench for modeling the processes of drilling waterjet channels: F-1—filter No1; F-2—filter No2; F-3—filter No3; F-4—filter No4; T-1—Tank; PR—pressure reducer; RC—rotary coupling; P-1–7—nanometer.  
pressure pump. Pump-1 high-pressure pump is powered by a 35 hp M gasoline engine. Downstream of Pump-1 high-pressure pump, the working agent, passing through the pressure reducer PR and the rotary coupling RC, enters the high-pressure hose (shown in the flow diagram with a thick red line). The high-pressure hose delivers the working agent to the waterjet nozzle (shown in the figure with a red arrow). This way, the flow of the working agent stimulates the rock samples at a high velocity of jets, thus creating holes using the method of waterjet drilling. The spent working agent is collected in the bottom sum; Pump-2 (drain pump) pumps it through the spent working agent purification unit consisting of two mechanical purification filters F-3 and F-4 connected in series. Structurally, the spent working agent purification unit is similar to the primary filtration unit. Downstream of the spent working agent purification unit, the working agent is fed back to the storage tank T-1.  
Table 1 shows technical characteristics of the main equipment and special tools used to create a laboratory high-pressure bench.  
The experiments studied the technological process of waterjet drilling with 6 different through-type waterjet nozzles with an overall size of 18.3 \(\times\) 31.3 mm, with different numbers and diameters of front and rear diffusers (holes). Table 2 shows the technical characteristics of the waterjet nozzles under consideration.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Item on the Process Flow Diagram** & **Technical Characteristics** \\ \hline H-1 & Maximum throughput 1260 L/h (21 L/min) \\  & Working pressure 480–500 bar \\ \hline Gasoline engine & Motor power 35 hp (25.74 kW) \\  & Fuel consumption 3.8 L/h \\ \hline  & & Hose length 100 m \\  & Inner diameter DN, 8 mm \\ Red line (high-pressure flexible hose) & Outer diameter, 14.5 mm \\  & Working pressure WP 600 bar \\  & Burst pressure BP 2400 bar \\ \hline \hline \end{tabular}
\end{table}
Table 1: Technical characteristics of the main equipment and special tools for a laboratory bench to model the processes of drilling waterjet channels.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Nozzle** & **Image of the** & **Number of Diffusers** & **Number of Diffusers** & **Ratio of the Area** \\
**Number** & **Manufactured** & **Nozzle Type** & **on the Front** & **on the Rear** & **of the Front** \\  & **Nozzle** & **Part/Diameter of One** & **Part/Diameter of One** & **Diffusers to the** \\  & & **Diffuser, mm** & **Diffuser, mm** & **Rear Diffusers** \\ \hline No.1 & & Through-type & 1/0.5 & 3/0.5 & 0.33 (3) \\ \hline No.2 & & Through-type & 1/0.5 & 3/1.0 & 0.083 (3) \\ \hline No.3 & & Through-type & 4/0.5 & 4/1.0 & 0.33 (3) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Technical characteristics of the waterjet nozzles under test.  
Modeling of radial channel drilling was carried out in aerated concrete blocks with density of 500 kg/m\({}^{3}\) and strength between 25-32 kg/cm\({}^{2}\).