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enmodes GmbH
engineeringmodeling
design
Second Heart ReportJuly 12, 2018
Dr. Fiete Böhning
Head of Engineering Services
+49 (0)241 41251073
+49 (0)176 78013798
enmodes GmbH
Wilhelmstraße 38
52070 Aachen
Germany
www.enmodes.de – engineering, modeling, design
Contact details
1
Overview of the device
CAD geometry provided by Second HeartImpeller diameter: 13.5 & 14.5 mmOpen stent (outer) diameter: 22.86 mm
2
Volume extraction
Tube around the deviceTube diameter: 22.86 mm
Extracted fluid volume for flow simulations
3
Boundary conditions
• Flow Inlet (L/min):3.5, 4.5 & 5.5
• Impeller Speeds (rpm):7500, 10500 & 15000
• Non-Newtonian Blood Model• Full 3D simulation
Inlet
Outlet
4
Analysis Results
∆P = Pressure outlet – Pressure inlet
RPM 15000; average increase in pressure head ≈ 31%
RPM 10500; average increase in pressure head ≈ 40%
RPM 7500; ; average increase in pressure head ≈ 66%
Impeller 13.5Impeller 14.5
5
General observations
Large back flow whirls above the impeller blades → reduces the efficiency
6
General observations
Continuous back flow along the impeller shaft → reduces the efficiency
7
General observations (Impeller – 14.5 mm)
High velocity and low pressures around the blade tip → potentially unnecessary high shear stresses
VelocityPressure
8
Comparison of Impellers
Impeller 14.5 mmImpeller 13.5 mm
9
Comparison of Impellers
Impeller 14.5 mmImpeller 13.5 mm
10
Impeller – 14.5 mm
11
Flow simulation – Flow 3.5 L/min at 10500 rpm
Plane 2
12
Flow simulation – Flow 4.5 L/min at 10500 rpm
Plane 2
13
Flow simulation – Flow 5.5 L/min at 10500 rpm
Plane 2
14
Velocity and Streamlines – Flow 3.5 L/min at 7500 rpm
15
Velocity and Streamlines – Flow 4.5 L/min at 7500 rpm
16
Velocity and Streamlines – Flow 5.5 L/min at 7500 rpm
17
Velocity and Streamlines – Flow 3.5 L/min at 10500 rpm
18
Velocity and Streamlines – Flow 4.5 L/min at 10500 rpm
19
Velocity and Streamlines – Flow 5.5 L/min at 10500 rpm
20
Velocity and Streamlines – Flow 3.5 L/min at 15000 rpm
21
Velocity and Streamlines – Flow 4.5 L/min at 15000 rpm
22
Velocity and Streamlines – Flow 5.5 L/min at 15000 rpm
23
Comparison of Flow: 3.5, 4.5 & 5.5 L/min at 10500 rpm
Back flow whirls are almost the same for all flow rate for a constant impeller speed.
24
Comparison of Speed: 7500, 10500 & 15000 rpm at 4.5 L/min
Back flow whirls increases with increase in impeller speed for a constant flow rate.
25
Impeller – 13.5 mm
next slides are as sent in the previous report
26
General observations (Impeller – 13.5 mm)
High velocity and low pressures around the blade tip → potentially unnecessary high shear stresses
VelocityPressure
27
Flow simulation – Flow 3.5 L/min at 10500 rpm
Plane 2
28
Flow simulation – Flow 4.5 L/min at 10500 rpm
Plane 2
29
Flow simulation – Flow 5.5 L/min at 10500 rpm
Plane 2
30
Velocity and Streamlines – Flow 3.5 L/min at 7500 rpm
31
Velocity and Streamlines – Flow 4.5 L/min at 7500 rpm
32
Velocity and Streamlines – Flow 5.5 L/min at 7500 rpm
33
Velocity and Streamlines – Flow 3.5 L/min at 10500 rpm
34
Velocity and Streamlines – Flow 4.5 L/min at 10500 rpm
35
Velocity and Streamlines – Flow 5.5 L/min at 10500 rpm
36
Velocity and Streamlines – Flow 3.5 L/min at 15000 rpm
37
Velocity and Streamlines – Flow 4.5 L/min at 15000 rpm
38
Velocity and Streamlines – Flow 5.5 L/min at 15000 rpm
39
Comparison of Flow: 3.5, 4.5 & 5.5 L/min at 10500 rpm
Back flow whirls decrease with increase in flow rate for a constant impeller speed.
40
Comparison of Speed: 7500, 10500 & 15000 rpm at 4.5 L/min
Back flow whirls increases with increase in impeller speed for a constant flow rate.
41
Summary
The current study was conducted for an impeller with blade diameters of 13.5 & 14.5 mm, in a tubewith the same outer diameter as that of the open stent, i.e. 22.86 mm. Simulations were carried out forconstant flow conditions.
Comparison of the two impellers:
• In general, the pressure head developed by the bigger 14.5 mm impeller is better than that of the13.5 mm impeller.
• The local hydraulic behaviour of the impellers are similar.
General observations (presented in earlier report):
• The current design of the Second Heart implantable device results in large back flows around the impeller reducing the efficiency ofthe device.
• It also has a potential for unnecessary high shear stresses around the impeller blades.
• The current analysis also does not provide any indicators for the device effectiveness in human anatomy with respect to pathologicalconditions, pulsatile flow conditions, device placement, etc.
• Further analysis & design optimization are needed to improve the device performance and its blood compatibility.